bluuebunny/crossref_metadata_2025 huggingface dataset:
Economic evaluation of Hereford cattle breeding schemes incorporating direct and indirect measures of feed intake
Authors: Kahi A. K. , Barwick S. A. , Graser H-U.
Published: October 2003

A deterministic approach was used to evaluate the effect of incorporating direct and indirect measures of feed intake as additional selection criteria in breeding schemes for Hereford cattle. A 2-tier nucleus breeding scheme consisting of a nucleus and a commercial sector was assumed. Four breeding objectives specific to Australian Hereford cattle were considered. These addressed production systems that targetted 4 markets (Domestic Supermarket, 'Hereford Prime', Short-fed Export, and Long-fed Export). The breeding objectives differed especially in the feed cost involved for differing amounts of grain finishing and in the extent to which marbling is valued by the market (from none to quite a lot). The breeding schemes evaluated differed in the measures available for use as selection criteria. The schemes ranged from one that utilised growth, scanned carcass and fertility criteria currently available to Australian cattle breeders (Scheme 1) to one which also incorporated residual feed intake (RFI) and blood serum insulin-like growth factor I (IGF-1) criteria (Scheme 5). The latter scheme included selection of sires for the nucleus using a 2-stage selection process, with a proportion of bulls selected after weaning for measurement of RFI. Schemes utilising either IGF-1 or RFI or both as criteria generated additional genetic gain and profitability for each breeding objective. Profit was optimal across all the Hereford cattle breeding objectives when the top 5% of bulls was measured for RFI after being selected on an index incorporating IGF-1 and other information available on the bull and its relatives at a young age. Further increase in the proportion of bulls measured for RFI for consideration in the second selection stage resulted in a slow decline in profit per cow in the population and a flat response in genetic gain. In the absence of more breed-specific information, these results may also have application in breeds other than Herefords.
Low temperature induced spikelet sterility in rice. I. Nitrogen fertilisation and sensitive reproductive period
Authors: Gunawardena T. A. , Fukai S. , Blamey F. P. C.
Published: October 2003

Low temperature during panicle development in rice increases spikelet sterility. This effect is exacerbated by high rates of nitrogen (N) application in the field. Spikelet sterility induced by low temperature and N fertilisation was examined in glasshouse experiments to clarify the mechanisms involved. In two glasshouse experiments, 12-h periods of low (18/13�C) and high (28/23�C) day/night temperatures were imposed over periods of 5–7 days during panicle development, to determine the effects of low temperature and N fertilisation on spikelet sterility. In one experiment, 50% sunlight was imposed together with low temperature to investigate the additive effects of reduced solar radiation and low temperature. The effect of increased tillering due to N fertilisation was examined by a tiller removal treatment in the same experiment. Pollen grain number and spikelet sterility were recorded at heading and harvest, respectively. Although there was no significant effect of low temperature on spikelet sterility in the absence of applied N, low temperature greatly increased spikelet sterility as a result of a reduction in the number of engorged pollen grains per anther in the presence of applied N. Spikelet sterility was strongly correlated with the number of engorged pollen grains per anther. Low temperature during very early (late stage of spikelet differentiation–pollen mother cell stage) and peak (second meiotic division stage–early stage of extine formation) microspore development caused a severe reduction in engorged pollen production mainly as a result of reduced total pollen production. Unlike low temperature, the effect of shading was rather small. The increased tillering due to application of high rates of N, increased both spikelet number per plant and spikelet sterility under low temperature conditions. The removal of tillers as they appeared reduced the number of total spikelets per plant and maintained a large number of engorged pollen grains per anther which, in turn, reduced spikelet sterility. The number of engorged pollen grains per anther determined the numbers of intercepted and germinated pollen grains on the stigma. It is concluded that N increased tillering and spikelet number per plant and this, in turn, reduced the number of engorged pollen grains per anther, leading into increased spikelet sterility under low temperature condition.
Low temperature induced spikelet sterility in rice. II. Effects of panicle and root temperatures
Authors: Gunawardena T. A. , Fukai S. , Blamey F. P. C.
Published: October 2003

Low temperatures impose restrictions on rice (Oryza sativa L.) production at high latitudes. This study is related to low temperature damage that can arise mid-season during the panicle development phase. The objective of this study was to determine whether low temperature experienced by the root, panicle, or foliage is responsible for increased spikelet sterility. In temperature-controlled glasshouse experiments, water depth, and water and air temperatures, were changed independently to investigate the effects of low temperature in the root, panicle, and foliage during microspore development on spikelet sterility. The total number of pollen and number of engorged pollen grains per anther, and the number of intercepted and germinated pollen grains per stigma, were measured. Spikelet sterility was then analysed in relation to the total number of pollen grains per spikelet and the efficiency with which these pollen grains became engorged, were intercepted by the stigma, germinated, and were involved in fertilisation. There was a significant combined effect of average minimum panicle and root temperatures on spikelet sterility that accounted for 86% of the variation in spikelet sterility. Total number of pollen grains per anther was reduced by low panicle temperature, but not by low root temperature. Whereas engorgement efficiency (the percentage of pollen grains that were engorged) was determined by both root and panicle temperature, germination efficiency (the percentage of germinated pollen grains relative to the number of engorged pollen grains intercepted by the stigma) was determined only by root temperature. Interception efficiency (i.e. percentage of engorged pollen grains intercepted by the stigma), however, was not affected by either root or panicle temperature. Engorgement efficiency was the dominant factor explaining the variation in spikelet sterility. It is concluded that both panicle and root temperature affect spikelet sterility in rice when the plant encounters low temperatures during the microspore development stage.
Yield response of restricted-tillering wheat to transient waterlogging on duplex soils
Authors: Condon A. G. , Giunta F.
Published: October 2003

Transient waterlogging during winter and spring reduces wheat yield in many parts of southern Australia. Yield reductions from waterlogging are associated with reduced production and survival of tillers, fewer and smaller fertile tillers, and smaller grain size. Under favourable conditions, wheats that have the tiller-inhibition ('tin') gene produce a lower total number of tillers but a higher proportion of large, productive tillers and larger grains than wheats without this gene. These characteristics of restricted-tillering wheat may contribute to improved yield under transient waterlogging. We compared the growth and yield of the commercial variety Bodallin and 2 Bodallin backcross derivatives containing the 'tin' gene in 8 field trials grown on shallow, duplex soils in 1995 and 1996 at 3 locations in the south-west of Western Australia. Trials were sown at standard (1995) and standard and high (1996) seeding rates. Trial-mean yield ranged from 0.5 to 4.7 t/ha, depending on the occurrence and severity of waterlogging before anthesis and of soil water deficit before and after anthesis. Grain yield of the restricted-tillering (RT) lines averaged only c. 80% of Bodallin. At all sites and seeding rates the RT lines had fewer spikes per m2 (45% fewer, on average) but averaged 44% more grains per spike. In 1996 only, grain weight of the RT lines was 6% greater than of Bodallin. There was no evidence that the relative yield of the RT lines was greater at waterlogged sites than at other sites. Waterlogging reduced the number of fertile spikes of RT lines and of Bodallin to the same relative extent and differences in grains per spike and grain size had little effect on relative yields. Even though harvest index of the RT lines was slightly elevated in some environments, biomass production of the RT lines was low in all environments. We conclude that wheats with the 'tin' gene are unlikely to have a yield advantage under transient waterlogging unless their biomass production can match that of more freely tillering wheats.
Syntheses and Crystal Structures of Silver(I) Organosulfur Polymers as One-Dimensional Chains
Authors: Wang Ruihu , Hong Maochun , Su Weiping , Cao Rong , Zhao Yingjun , Weng Jiabao
Published: October 2003

Two silver(I) organosulfur coordination polymers, {[Ag2(mbpsq).dmf](NO3)2}n (1) and {[Ag3(bpsp)2(CH3CN)]-(BF4)3.2 H2O}n (2), were prepared by self-assembly of silver(I) with the chelating heterocyclic ligands mbpsq and bpsp (mbpsq = 2,3-bis[2-(4-methylpyrimidinyl)methylsulfanyl]-quinoxaline; bpsp = 2,6-bis[(2-pyrimidinyl)-methylsulfanyl]-pyridine). Single-crystal X-ray diffraction analysis reveals that (1) crystallizes in the triclinic space group P1– with a 10.1937(8), b 11.2160(9), c 13.8445(11) Å, α 103.0620(10), β 106.4850(10), γ; 96.2720(10)°, V 1452.8(2) Å3, Z 2. Each mbpsq molecule acts as a hexadentate ligand, in which two nitrogen atoms of the quinoxaline ring and adjacent sulfur atoms form two stable five-membered rings and two nitrogen atoms from different methylpyrimidine rings bridge two silver(I) centers to form a one-dimensional chain structure. Complex (2) crystallizes also in the triclinic space group P1– with a 12.8119(3), b 13.8902(4), c 15.4534(5) Å, α 70.6980(10), β 68.7570(10), γ; 85.3380(10)°, V 2416.83(12) Å3, Z 2. The bpsq molecules act as tridentate and tetradentate ligands ligating three silver(I) centres of different coordination environments to form a one-dimensional zigzag chain.
Valence Bond Studies of N2F+
Authors: Harcourt Richard D.
Published: October 2003

The results of STO-6G valence bond (VB) calculations for the linear cation N2F+ show that (a) the dominant Lewis-type VB structures involve a single positive charge which is located on either of the nitrogen atoms, and (b) a small amount of N–F π-bonding arises primarily from the formation of one-electron N–F π-bonds. It is suggested that N–F π-bonding is one of several factors which are responsible for the shortening of the N–F bond of N2F+ relative to that of NF4+. Valence bond and bond length considerations imply that the extent of N–O π-bonding in N2O and NO43- exceeds the degree of N–F π-bonding in N2F+ and NF4+.
Selected Sulfonyl Compounds as Anticancer/Antimalarial Agents
Authors: Langler Richard F. , Paddock Robert L. , Thompson David B. , Crandall Ian , Ciach Michelle , Kain Kevin C.
Published: October 2003

The synthesis and biological testing of a series of sulfonyl phenols and sulfonyl aryl methyl ethers has revealed that p-methoxyphenyl p-toluenesulfonate is a very selective and effective antimalarial agent which shows pronounced activity against human skin cancer cells. Application of a counter-attack strategy permits the direct preparation of the requisite tosylate ether from the bis(tosylate) of dihydroquinone.
New Macrocyclic Ligands. XVI. Synthesis of a Series of N-Benzylated Macrocycles Incorporating N4O2-Donor Set
Authors: Fenton Ronald R. , Lindoy Leonard F. , Price Jason R. , Skelton Brian W. , White Allan H.
Published: October 2003

The synthesis of five 20-membered, N-benzylated macrocyclic ligands incorporating N4O2-donor sets and from one to three benzyl substituents for use in metal-ion recognition studies is described. The new derivatives were obtained by both benzylation of the pre-formed parent macrocycle using benzyl chloride in acetonitrile in the presence of base or, in one case, by performing macrocyclic ring closure using the appropriate N-benzylated triamine precursor by means of a bis-Schiff base condensation with the corresponding dialdehyde, followed by in situ reduction of the diamine linkages so formed. The single crystal X-ray structure of the symmetrically substituted, di-N-benzylated derivative is reported.
Effect of Cyclodextrins on Electrophilic Aromatic Bromination in Aqueous Solution
Authors: Dumanski Paul G. , Easton Christopher J. , Lincoln Stephen F. , Simpson Jamie S.
Published: October 2003

Cyclodextrins act as molecular reactors to change the ratios of the products of reactions of anisole, acetanilide, 3-methylanisole, and 3-methylacetanilide with pyridinium dichlorobromate. With anisole and acetanilide, bromination at the para position is favoured over ortho substitution, and the effect is greatest with α-cyclodextrin. In the reactions of the methylanisole and methylacetanilide, the cyclodextrins afford higher yields of monobrominated products and less of the di- and tribromides, and β-cyclodextrin has the greatest effect. These outcomes can be attributed to inclusion of the substrates within the cyclodextrins restricting access of the reagent adjacent to the methoxy and acetamido groups. The yields of 4-bromoanisole, 4-bromoacetanilide, 4-bromo-3-methylanisole, and 4-bromo-3-methylacetanilide are thus increased from 73 to 94, 55 to 98, 37 to 86, and 39 to 72%, respectively. Perhaps more significantly, the quantities of the corresponding by-products are substantially reduced, from 27 to 6, 45 to 2, 63 to 14, and 61 to 28%. Since the reactions occur readily in water at ambient temperature, the cyclodextrins make them very efficient.
Preparation of Selectively Protected L-Dopa Derivatives: Oxidation of Tyrosine-3-boronates
Authors: Hunter Luke , Hutton Craig A.
Published: October 2003

Conversion of 3-iodo-L-tyrosine to protected tyrosine-3-boronate esters, followed by oxidation with hydrogen peroxide, provides a mild and efficient method for the preparation of selectively protected L-dopa derivatives.
Are high lupin seeding rates more risky in the Western Australian wheatbelt?
Authors: O'Connell M. , Pannell D. J. , French R. J.
Published: October 2003

A seeding rate aimed at establishing 45 plants/m2 has been the long-standing recommendation for lupin crops in Western Australia. However, contrary to recommendations, many farmers in low rainfall areas of the state use a seeding rate that results in densities as low as 25–30 plants/m2, claiming that these rates give more reliable yields. Current recommendations for optimal lupin seeding rates are based solely on maximisation of expected profit and risk preferences have not been considered. The present study tested the hypothesis that optimal lupin seeding rates are lower if the farmer is averse to risk. A risk analysis of lupin yields in response to seeding rates was conducted to determine whether optimal seeding rates are lower for farmers who are risk averse. The analysis was based on results from field trials from various locations in Western Australia in various years. Lupin yields were not less reliable at high seeding rates and therefore risk aversion does not materially reduce the optimal seeding rate. Farmers who used a seeding rate lower than the recommended rate forewent profit without lowering risk. In the low and medium rainfall areas, the average reduction in expected gross margin from using a suboptimum seeding rate (25–30 plants/m2) is AU$4–10/ha. Farmers in the high rainfall zone who aim for 25–30 plants/m2 could forego in excess of $30/ha, particularly in situations where high yields are possible.
Dry matter yield, forage quality and persistence of tall fescue (Festuca arundinacea) cultivars compared with perennial ryegrass (Lolium perenne) in a subtropical environment
Authors: Callow M. N. , Lowe K. F. , Bowdler T. M. , Lowe S. A. , Gobius N. R.
Published: October 2003

The dry matter (DM) yield, plant persistence and forage quality of tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne) were compared in the subtropical environment of southern Queensland, Australia. The field study was conducted under irrigation with pure, nitrogen fertilised stands of 10 commercial tall fescue cultivars (Advance, AU Triumph, Bombina, Cajun, Dovey, Maximise, Midwin, Torpedo, Quantum and Vulcan), 3 experimental cultivars (ITF 97010, ITF 97020 and PWF 29) and Dobson perennial ryegrass. From July 1997, plots were defoliated at 4-week intervals for 3 years. Changes in crude protein content and in vitro DM digestibility (IVDMD) were determined at 1, 2, 3, 4, 6 and 8 weeks post-defoliation in October (spring) 1997, January (summer), March (autumn), June (winter) and September (spring) 1998.Some cultivars of irrigated tall fescue were shown to be better adapted to a subtropical environment than perennial ryegrass. After 3 years, cumulative DM yields were in excess of 30 t/ha for Dovey, Quantum, ITF 97010, AU Triumph and Cajun tall fescue compared with 12 t/ha from Dobson perennial ryegrass swards.Plant development had a considerable influence on crude protein content and IVDMD of tall fescue and perennial ryegrass, more so than the length of the regrowth period. As plant tissue matured, the forage quality during spring declined linearly for crude protein content and for IVDMD (1998 only), and declined exponentially for IVDMD during spring (1997), summer, autumn and winter (1998). Quality losses may be minimised if tall fescue cultivars are defoliated every 2–3 weeks during spring and summer and every 3–4 weeks during autumn and winter.
Yield responses to ethephon for unshaken and mechanically shaken macadamia
Authors: Trueman S. J.
Published: October 2003

Ethephon promotes fruit abscission and accelerates harvest of macadamia, Macadamia integrifolia (Proteaceae), but has limited use due to concerns that associated abscission of inner-canopy leaves may reduce subsequent yield and nut quality. Yield and quality were monitored for 2 years following ethephon application to both unshaken and mechanically shaken trees of the late-abscising cultivar, A16. Nut quality was not adversely affected in subsequent seasons, but effects on yield varied. In 3 of 6 experiments, ethephon reduced yield in the year after application. However, in 4 of the 6 experiments, 2 years of ethephon application greatly elevated yield in the third year. This was not a compensating recovery from low second-year yield, as third-year yield of trees that received only 1 ethephon treatment did not differ from yield of control trees. Ethephon-assisted harvest remains feasible for macadamia, although further work is warranted given the potential risks and considerable benefits for subsequent yield. Inner canopy defoliation, resulting from ethephon use, could represent a canopy management technique for dense-canopy fruit trees.
Somatic hybridisation for improvement of citrus rootstock: production of five new combinations with potential for improved disease resistance
Authors: Costa M. A. Pereira de Carvalho , Mendes B. M. J. , Filho F. A. A. Mourão
Published: October 2003

The development of biotechnological tools such as protoplast fusion has provided a means of bypassing natural barriers related to reproductive biology of citrus found in conventional breeding systems. We report the production of 4 interspecific somatic hybrids, Cleopatra mandarin + Volkamer lemon, Ruby Blood sweet orange + Volkamer lemon, Rohde Red Valencia sweet orange + Volkamer lemon, and Rangpur lime + Sunki mandarin, and 1 intergeneric somatic hybrid, Valencia sweet orange + Fortunella obovata (Tanaka), which may be included and evaluated in rootstock improvement programs. Protoplasts were isolated from embryogenic calli and seedling leaves, and chemically fused with polyethylene glycol. Plants were regenerated via somatic embryogenesis and somatic hybridisation was confirmed by foliar morphology, cytological and DNA (RAPD) analyses. Somatic hybrids may combine required rootstock characteristics such as tolerance to citrus blight, tristeza virus, and Phytophthora, and have potential for control of tree size due to polyploidy.
A survey of Sigatoka leaf disease (Mycosphaerella musicola Leach) of banana and soil calcium levels in North Queensland
Authors: Gerald S. M. Fitz , White S. D. , Dickinson A. A. , Goldman B.
Published: October 2003

Annual averages of lesion development of yellow Sigatoka caused by Mycosphaerella musicola were calculated from surveys conducted at 14-day intervals for 57 banana sites in the North Queensland production region situated in the wet tropics between Cardwell and Innisfail. Soil up to 250 mm depth was sampled from sites between March 2000 and September 2001. Soil parameters were compared with 12 months of leaf disease data averaged centrally about the time the soil sample was taken. The 4 different formulas for calcium expression tested all proved to be significant predictors of disease levels. The strongest relationship (r2 = 0.229) between soil calcium levels and disease levels was obtained from a formula based on an Albrecht interpretation of the soil test data, which includes a pH-derived estimation of exchangeable hydrogen in the denominator. A Chi square analysis on a model incorporating calcium and soil boron was statistically significant (P<0.001). The model combining calcium and boron levels explained more variation in disease levels than calcium alone. Variation in other factors influencing disease such as fungicide program, weather conditions, soil moisture conditions and crop stage may account for variation in disease levels at low calcium sites.
Osmotic adjustment and seed yield of Brassica napus and B. juncea genotypes in a water-limited environment in south-western Australia
Authors: Niknam S. R. , Ma Q. , Turner D. W.
Published: October 2003

The relationship between osmotic adjustment and seed yield of Brassica oilseeds was examined at a low rainfall site, Merredin, Western Australia, in 1998 and 1999. Genotypes of B. napus and B. juncea were subjected to rain-fed and irrigated treatments at the seed-fill stage. The B. juncea lines showed small or even no yield reduction under rain-fed conditions, and generally had no yield advantage over the B. napus cultivars where irrigated. In both species, an inverse correlation was found between the magnitude of osmotic adjustment and the percentage of yield reduction. Genotypes with low osmotic adjustment, under rain-fed conditions, had a yield reduction of up to 40%, whereas those with high osmotic adjustment had only 0–10% yield reduction. In contrast, seed oil concentrations decreased from 41% under irrigation to 38% under water deficits and the differences among genotypes were not related to osmotic adjustment. In 1999, osmotic adjustment was again observed for most of the genotypes, but its association with seed yield was not as obvious as in the previous year and usually only the osmotically adjusting B. juncea genotypes maintained a good yield under water deficits. Not all the B. juncea genotypes expressed osmotic adjustment despite the fact that they were generally more drought resistant than the B. napus genotypes. In both years, however, osmotic adjustment was associated with increased harvest indices of B. napus and B. juncea, indicating that this physiological trait can be beneficial to Brassica yield in a water-limited Mediterranean-type environment.
Growth, seed set and nitrogen fixation of 28 annual legume species on 3 Vertosol soils in southern New South Wales
Authors: Dear B. S. , Sandral G. A. , Peoples M. B. , Wilson B. C. D. , Taylor J. N. , Rodham C. A.
Published: October 2003

The adaptation of 28 annual legume species to heavy clay cracking soils prone to waterlogging during winter was evaluated at 3 sites ranging in pH (CaCl2) from 4.6 to 5.4 in the wheatbelt of southern NSW. The 32 accessions and cultivars included Medicago arabica, M. polymorpha, Melilotus albus (syn. M. alba), Trigonella balansae, and 24 Trifolium species. Species identified as potentially valuable new plants for these environments included Trifolium hirtum, T. echinatum, T. glanduliferum and M. arabica for winter production, and M. albus, T. echinatum, T. glanduliferum, T. isthmocarpum, T. pauciflorum, and T. purpureum for spring production. Current cultivars of T. subterraneum subsp. brachycalycinum cv. Clare, and subsp. yanninicum, cv. Riverina, T. resupinatum cvv. Kyambro, Nitro and Prolific, and T. michelianum cvv. Bolta and Paradana, and M. polymorpha cv. Santiago, also proved well adapted. Average seed mass (size) of the legume species varied from 0.3 mg to 8.9 mg/seed with a negative curvilinear relationship between individual seed mass of a species and the number of seed set at all 3 sites (r2 = 0.59–0.89). Seed mass of a species did not influence winter productivity or seed yield. The percentage of nitrogen biologically fixed by the individual species in the first year averaged over the 3 sites varied from 30 to 75%. Species which fixed the highest proportion of their nitrogen requirement were T. subterraneum, M. arabica, T. isthmocarpum and T. resupinatum cv. Kyambro, all fixing >62% of their shoot nitrogen and having a nitrogen content >3.0%. In contrast, T. sylvaticum, T. cherleri, T. spumosum, T. stellatum and T. glomeratum performed poorly at most sites, and fixed <42% of their nitrogen requirements (averaged over 3 sites) with <2.5% nitrogen in their tissue in spring.
Single and coastal superphosphates are equally effective as sulfur fertilisers for subterranean clover on very sandy soils in high rainfall areas of south-western Australia
Authors: Bolland M. D. A. , Yeates J. S. , Clarke M. F.
Published: October 2003

To reduce leaching of phosphorus (P) from fertilised pastures to shallow estuaries in the high rainfall (>800 mm annual average) areas of south-western Australia, and to supply extra sulfur (S) for subterranean clover (Trifolium subterraneum L.) in pasture, 'coastal superphosphate' was developed as a possible alternative P and S fertiliser to single superphosphate. Coastal superphosphate is made by adding phosphate rock and elemental S to single superphosphate as it comes out of the den before granulation. It has about 3 times more sulfur (S) and one-third the water-soluble P content than single superphosphate. Four long-term (5-year) field experiments were conducted in south-western Australia to compare the effectiveness of single and coastal superphosphate as S fertilisers for subterranean clover pasture grown on very sandy soils that are frequently S deficient after July each year due to leaching of S from soil. Seven different amounts of S were applied as fertiliser annually. Fertiliser effectiveness was assessed from clover herbage yield and S concentration in dried herbage. Fertiliser nitrogen was not applied in these experiments as this was the normal practice for pastures in the region when the research was conducted.Both coastal and single superphosphates were equally effective per unit of applied S for producing dried clover herbage and increasing S concentration in herbage. Previous research on very sandy soils in the region had shown that coastal superphosphate was equally or more effective per unit of applied P for production of subterranean clover herbage. It is, therefore, concluded that coastal superphosphate is a suitable alternative S and P fertiliser for clover pastures on very sandy soils in the region. The concentration of S in dried clover herbage that was related to 90% of the maximum yield (critical S) was about 0.20–0.35% S during August (before flowering) and 0.15–0.20% S during October (after flowering).
Production of betaine from Australian Melaleuca spp. for use in agriculture to reduce plant stress
Authors: Naidu B. P.
Published: October 2003

Some of the Melaleuca spp., native to Australia, are unique in their ability to withstand environmental stresses. The stress tolerance of these species is attributable to their ability to accumulate large quantities of organic compounds known as osmoprotectants or proline (betaine) analogues. Osmoprotectants can be extracted easily from these plants and used in seed treatment and foliar application to increase the stress tolerance of economic crops. This paper examines the potential of 8 Melaleuca spp. for the production of osmoprotectants. Melaleuca bracteata, which accumulates the proline analogue trans 4-hydroxy-N-methyl proline (MHP), was the most vigorous of all 8 species field tested in New South Wales and Queensland. A simple extraction protocol for commercial use is suggested. By growing M. bracteata, it is possible to achieve an average yield of 493 kg/ha of MHP along with 218 kg/ha of essential oil, with a gross economic return of AU$14505/ha. This return is better than that estimated for M. alternifolia, $3200/ha, which is currently grown for the production of tea tree oil. The cultivation of M. bracteata has the potential of creating a new industry for Australia, in addition to its positive role in the control of dryland salinity.
Differential regulation of midbrain dopaminergic neuron development by Wnt-1, Wnt-3a, and Wnt-5a
Authors: Castelo-Branco Gonçalo , Wagner Joseph , Rodriguez Francisco J. , Kele Julianna , Sousa Kyle , Rawal Nina , Pasolli Hilda Amalia , Fuchs Elaine , Kitajewski Jan , Arenas Ernest
Published: October 2003

The Wnts are a family of glycoproteins that regulate cell proliferation, fate decisions, and differentiation. In our study, we examined the contribution of Wnts to the development of ventral midbrain (VM) dopaminergic (DA) neurons. Our results show that β-catenin is expressed in DA precursor cells and that β-catenin signaling takes place in these cells, as assessed in TOPGAL [Tcf optimal-promoter β-galactosidase] reporter mice. We also found that Wnt-1, -3a, and -5a expression is differentially regulated during development and that partially purified Wnts distinctively regulate VM development. Wnt-3a promoted the proliferation of precursor cells expressing the orphan nuclear receptor-related factor 1 (Nurr1) but did not increase the number of tyrosine hydroxylase-positive neurons. Instead, Wnt-1 and -5a increased the number of rat midbrain DA neurons in rat embryonic day 14.5 precursor cultures by two distinct mechanisms. Wnt-1 predominantly increased the proliferation of Nurr1+ precursors, up-regulated cyclins D1 and D3, and down-regulated p27 and p57 mRNAs. In contrast, Wnt-5a primarily increased the proportion of Nurr1+ precursors that acquired a neuronal DA phenotype and up-regulated the expression of Ptx3 and c-ret mRNA. Moreover, the soluble cysteine-rich domain of Frizzled-8 (a Wnt inhibitor) blocked endogenous Wnts and the effects of Wnt-1 and -5a on proliferation and the acquisition of a DA phenotype in precursor cultures. These findings indicate that Wnts are key regulators of proliferation and differentiation of DA precursors during VM neurogenesis and that different Wnts have specific and unique activity profiles.
Capture of an intermediate in the catalytic cycle of
l
-aspartate-β-semialdehyde dehydrogenase
Authors: Blanco Julio , Moore Roger A. , Viola Ronald E.
Published: October 2003

The structural analysis of an enzymatic reaction intermediate affords a unique opportunity to study a catalytic mechanism in extraordinary detail. Here we present the structure of a tetrahedral intermediate in the catalytic cycle of aspartate-β-semialdehyde dehydrogenase (ASADH) from
Haemophilus influenzae
at 2.0-Å resolution. ASADH is not found in humans, yet its catalytic activity is required for the biosynthesis of essential amino acids in plants and microorganisms. Diaminopimelic acid, also formed by this enzymatic pathway, is an integral component of bacterial cell walls, thus making ASADH an attractive target for the development of new antibiotics. This enzyme is able to capture the substrates aspartate-β-semialdehyde and phosphate as an active complex that does not complete the catalytic cycle in the absence of NADP. A distinctive binding pocket in which the hemithioacetal oxygen of the bound substrate is stabilized by interaction with a backbone amide group dictates the
R
stereochemistry of the tetrahedral intermediate. This pocket, reminiscent of the oxyanion hole found in serine proteases, is completed through hydrogen bonding to the bound phosphate substrate.
DNA-repair protein hHR23a alters its protein structure upon binding proteasomal subunit S5a
Authors: Walters Kylie J. , Lech Patrycja J. , Goh Amanda M. , Wang Qinghua , Howley Peter M.
Published: October 2003

The Rad23 family of proteins, including the human homologs hHR23a and hHR23b, stimulates nucleotide excision repair and has been shown to provide a novel link between proteasome-mediated protein degradation and DNA repair. In this work, we illustrate how the proteasomal subunit S5a regulates hHR23a protein structure. By using NMR spectroscopy, we have elucidated the structure and dynamic properties of the 40-kDa hHR23a protein and show it to contain four structured domains connected by flexible linker regions. In addition, we reveal that these domains interact in an intramolecular fashion, and by using residual dipolar coupling data in combination with chemical shift perturbation analysis, we present the hHR23a structure. By itself, hHR23a adopts a closed conformation defined by the interaction of an N-terminal ubiquitin-like domain with two ubiquitin-associated domains. Interestingly, binding of the proteasomal subunit S5a disrupts the hHR23a interdomain interactions and thereby causes it to adopt an opened conformation.
Evolutionary specialization of a tryptophan indole group for transition-state stabilization by eukaryotic transglutaminases
Authors: Iismaa Siiri E. , Holman Sara , Wouters Merridee A. , Lorand Laszlo , Graham Robert M. , Husain Ahsan
Published: October 2003

Covalent posttranslational protein modifications by eukaryotic transglutaminases proceed by a kinetic pathway of acylation and deacylation. Ammonia is released as the acylenzyme is formed, whereas the cross-linked product is released later in the deacylation step. Superposition of the active sites of transglutaminase type 2 (TG2) and the structurally related cysteine protease, papain, indicates that in the formation of tetrahedral intermediates, the backbone nitrogen of the catalytic Cys-277 and the Nε1 nitrogen of Trp-241 of TG2 could contribute to transition-state stabilization. The importance of this Trp-241 side chain was demonstrated by examining the kinetics of dansylcadaverine incorporation into a model peptide. Although substitution of the Trp-241 side chain with Ala or Gly had only a small effect on the Michaelis constant
K
m
(1.5-fold increase), it caused a >300-fold lowering of the catalytic rate constant
k
cat
. The wild-type and mutant TG2-catalyzed release of ammonia showed kinetics similar to the kinetics for the formation of cross-linked product, indicating that transition-state stabilization in the acylation step was rate-limiting. In papain, a Gln residue is at the position of TG2-Trp-241. The conservation of Trp-241 in all eukaryotic transglutaminases and the finding that W241Q-TG2 had a much lower
k
cat
than wild-type enzyme suggest evolutionary specialization in the use of the indole group. This notion is further supported by the observation that transition-state-stabilizing side chains of Tyr and His that operate in some serine and metalloproteases only partially substituted for Trp.
Olivo-cerebellar cluster-based universal control system
Authors: Kazantsev V. B. , Nekorkin V. I. , Makarenko V. I. , Llinás R.
Published: October 2003

The olivo-cerebellar network plays a key role in the organization of vertebrate motor control. The oscillatory properties of inferior olive (IO) neurons have been shown to provide timing signals for motor coordination in which spatio-temporal coherent oscillatory neuronal clusters control movement dynamics. Based on the neuronal connectivity and electrophysiology of the olivo-cerebellar network we have developed a general-purpose control approach, which we refer to as a universal control system (UCS), capable of dealing with a large number of actuator parameters in real time. In this UCS, the imposed goal and the resultant feedback from the actuators specify system properties. The goal is realized through implementing an architecture that can regulate a large number of parameters simultaneously by providing stimuli-modulated spatio-temporal cluster dynamics.
Processive phosphorylation of alternative splicing factor/splicing factor 2
Authors: Aubol Brandon E. , Chakrabarti Sutapa , Ngo Jacky , Shaffer Jennifer , Nolen Brad , Fu Xiang-Dong , Ghosh Gourisankar , Adams Joseph A.
Published: October 2003

SR proteins, named for their multiple arginine/serine (RS) dipeptide repeats, are critical components of the spliceosome, influencing both constitutive and alternative splicing of pre-mRNA. SR protein function is regulated through phosphorylation of their RS domains by multiple kinases, including a family of evolutionarily conserved SR protein-specific kinases (SRPKs). The SRPK family of kinases is unique in that they are capable of phosphorylating repetitive RS domains with remarkable specificity and efficiency. Here, we carried out kinetic experiments specially developed to investigate how SRPK1 phosphorylates the model human SR protein, ASF/SF2. By using the start–trap strategy, we monitored the progress curve for ASF/SF2 phosphorylation in the absence and presence of an inhibitor peptide directed at the active site of SRPK1. ASF/SF2 modification is not altered when the inhibitor peptide (trap) is added with ATP (start). However, when the trap is added first and allowed to incubate for a specific delay time, the decrease in phosphate content of the enzyme–substrate complex follows a simple exponential decline corresponding to the release rate of SRPK1. These data demonstrate that SRPK1 phosphorylates a specific region within the RS domain of ASF/SF2 by using a fully processive catalytic mechanism, in which the splicing factor remains “locked” onto SRPK1 during RS domain modification.
Bias and error in estimates of equilibrium free-energy differences from nonequilibrium measurements
Authors: Gore Jeff , Ritort Felix , Bustamante Carlos
Published: October 2003

In 1997, Jarzynski proved a remarkable equality that allows one to compute the equilibrium free-energy difference Δ
F
between two states from the probability distribution of the nonequilibrium work
W
done on the system to switch between the states,
e
–Δ

F

/kT
= 〈
e
–

W

/kT
〉, [Jarzynski, C. (1997)
Phys. Rev. Lett.
87, 2690–2693]. The Jarzynski equality provides a powerful free-energy difference estimator from a set of
N
irreversible experiments and is closely related to free-energy perturbation, a common computational technique for estimating free-energy differences. Despite the many applications of the Jarzynski estimator, its behavior is only poorly understood. In this article we derive the large
N
limit for the Jarzynski estimator bias, variance, and mean square error that is correct for arbitrary perturbations. We then analyze the properties of the Jarzynski estimator for all
N
when the probability distribution of work values is Gaussian, as occurs, for example, in the near-equilibrium regime. This allows us to quantitatively compare it to two other free-energy difference estimators: the mean work estimator and the fluctuation–dissipation theorem estimator. We show that, for near-equilibrium switching, the Jarzynski estimator is always superior to the mean work estimator and is even superior to the fluctuation–dissipation estimator for small
N.
The Jarzynski-estimator bias is shown to be the dominant source of error in many cases. Our expression for the bias is used to develop a bias-corrected Jarzynski free-energy difference estimator in the near-equilibrium regime.
Crystal structure of the tyrosine kinase domain of the hepatocyte growth factor receptor c-Met and its complex with the microbial alkaloid K-252a
Authors: Schiering Nikolaus , Knapp Stefan , Marconi Marina , Flocco Maria M. , Cui Jean , Perego Rita , Rusconi Luisa , Cristiani Cinzia
Published: October 2003

The protooncogene c-met codes for the hepatocyte growth factor receptor tyrosine kinase. Binding of its ligand, hepatocyte growth factor/scatter factor, stimulates receptor autophosphorylation, which leads to pleiotropic downstream signaling events in epithelial cells, including cell growth, motility, and invasion. These events are mediated by interaction of cytoplasmic effectors, generally through Src homology 2 (SH2) domains, with two phosphotyrosine-containing sequence motifs in the unique C-terminal tail of c-Met (supersite). There is a strong link between aberrant c-Met activity and oncogenesis, which makes this kinase an important cancer drug target. The furanosylated indolocarbazole K-252a belongs to a family of microbial alkaloids that also includes staurosporine. It was recently shown to be a potent inhibitor of c-Met. Here we report the crystal structures of an unphosphorylated c-Met kinase domain harboring a human cancer mutation and its complex with K-252a at 1.8-Å resolution. The structure follows the well established architecture of protein kinases. It adopts a unique, inhibitory conformation of the activation loop, a catalytically noncompetent orientation of helix αC, and reveals the complete C-terminal docking site. The first SH2-binding motif (
1349
YVHV) adopts an extended conformation, whereas the second motif (
1356
YVNV), a binding site for Grb2-SH2, folds as a type II β-turn. The intermediate portion of the supersite (
1353
NATY) assumes a type I β-turn conformation as in an Shc–phosphotyrosine binding domain peptide complex. K-252a is bound in the adenosine pocket with an analogous binding mode to those observed in previously reported structures of protein kinases in complex with staurosporine.
A presenilin dimer at the core of the γ-secretase enzyme: Insights from parallel analysis of Notch 1 and APP proteolysis
Authors: Schroeter Eric H. , Ilagan Ma. Xenia G. , Brunkan Anne L. , Hecimovic Silva , Li Yue-ming , Xu Min , Lewis Huw D. , Saxena Meera T. , De Strooper Bart , Coonrod Archie , Tomita Taisuke , Iwatsubo Takeshi , Moore Chad L. , Goate Alison , Wolfe Michael S. , Shearman Mark , Kopan Raphael
Published: October 2003

Notch receptors and the amyloid precursor protein are type I membrane proteins that are proteolytically cleaved within their transmembrane domains by a presenilin (PS)-dependent γ-secretase activity. In both proteins, two peptide bonds are hydrolyzed: one near the inner leaflet and the other in the middle of the transmembrane domain. Under saturating conditions the substrates compete with each other for proteolysis, but not for binding to PS. At least some Alzheimer's disease-causing PS mutations reside in proteins possessing low catalytic activity. We demonstrate (
i
) that differentially tagged PS molecules coimmunoprecipitate, and (
ii
) that PS N-terminal fragment dimers exist by using a photoaffinity probe based on a transition state analog γ-secretase inhibitor. We propose that γ-secretase contains a PS dimer in its catalytic core, that binding of substrate is at a site separate from the active site, and that substrate is cleaved at the interface of two PS molecules.
The genome of Nanoarchaeum equitans: Insights into early archaeal evolution and derived parasitism
Authors: Waters Elizabeth , Hohn Michael J. , Ahel Ivan , Graham David E. , Adams Mark D. , Barnstead Mary , Beeson Karen Y. , Bibbs Lisa , Bolanos Randall , Keller Martin , Kretz Keith , Lin Xiaoying , Mathur Eric , Ni Jingwei , Podar Mircea , Richardson Toby , Sutton Granger G. , Simon Melvin , Söll Dieter , Stetter Karl O. , Short Jay M. , Noordewier Michiel
Published: October 2003

The hyperthermophile
Nanoarchaeum equitans
is an obligate symbiont growing in coculture with the crenarchaeon
Ignicoccus
. Ribosomal protein and rRNA-based phylogenies place its branching point early in the archaeal lineage, representing the new archaeal kingdom Nanoarchaeota. The
N. equitans
genome (490,885 base pairs) encodes the machinery for information processing and repair, but lacks genes for lipid, cofactor, amino acid, or nucleotide biosyntheses. It is the smallest microbial genome sequenced to date, and also one of the most compact, with 95% of the DNA predicted to encode proteins or stable RNAs. Its limited biosynthetic and catabolic capacity indicates that
N. equitans
' symbiotic relationship to
Ignicoccus
is parasitic, making it the only known archaeal parasite. Unlike the small genomes of bacterial parasites that are undergoing reductive evolution,
N. equitans
has few pseudogenes or extensive regions of noncoding DNA. This organism represents a basal archaeal lineage and has a highly reduced genome.
Expression of T cell receptor βlocus in central nervous system neurons
Authors: Syken Josh , Shatz Carla J.
Published: October 2003

MHC class I proteins are cell-surface ligands that bind to T cell receptors and other immunoreceptors and act to regulate the activation state of immune cells. Recent work has shown that MHC class I genes and CD3ζ, an obligate component of T cell receptors, are expressed in neurons, are regulated by neuronal activity, and function in neuronal development and plasticity. A search for additional neuronally expressed T cell receptor components has revealed that the T cell antigen receptor β (TCRβ) locus is expressed in neurons of the murine central nervous system and that this expression is dynamically regulated over development. In neonates, expression is most abundant in various thalamic nuclei. At later ages and in adults, thalamic expression fades and cortical expression is robust, particularly in layer 6. In T cells, protein-encoding transcripts are produced only after recombination of the TCRβ genomic locus, which joins variable, diversity, and joining regions, a process that creates much of the diversity of the immune system. We detect no genomic recombination in neurons. Rather, transcripts begin in regions upstream of several joining regions, and are spliced to constant region segments. One of the transcripts encodes a hypothetical 207-aa, 23-kDa protein, which includes the TCRβ J2.7 region, and the entire C region. These observations suggest that TCRβ may function in neurons.
Fast protein folding kinetics
Authors: Schonbrun Jack , Dill Ken A.
Published: October 2003

Proteins are complex molecules, yet their folding kinetics is often fast (microseconds) and simple, involving only a single exponential function of time (called two-state kinetics). The main model for two-state kinetics has been transition-state theory, where an energy barrier defines a slow step to reach an improbable structure. But how can barriers explain fast processes, such as folding? We study a simple model with rigorous kinetics that explains the high speed instead as a result of the microscopic parallelization of folding trajectories. The single exponential results from a separation of timescales; the parallelization of routes is high at the start of folding and low thereafter. The ensemble of rate-limiting chain conformations is different from in transition-state theory; it is broad, overlaps with the denatured state, is not aligned along a single reaction coordinate, and involves well populated, rather than improbable, structures.