bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of gene regulation in growing pollen tubes of angiosperm and gymnosperm species using microprojectile bombardment
Authors: Martinussen Inger , Bate Neil , Weterings Koen , Junttila Olavi , Twell David
Published: May 2006

A microprojectile based transient expression assay was used to investigate the functional conservation of gene regulatory mechanisms in the male gametophytes of an angiosperm (Nicotiana tabacum) and two gymnospermous (Picea abies and Pinus pinaster) species. The activities of two angiosperm gene promoters, which have previously shown to be either preferentially expressed in the male gametophyte (lat52) or highly expressed in both the sporophyte and male gametophyte (ActI), were analysed. The results showed that in P. abies and P. pinaster, activity of the Act1 promoter was significantly higher than the activity of the lat52 promoter, while the converse was observed in N. tabacum. Detailed analysis of lat52 5’promoter deletions demonstrated that although the minimal ‐67 bp lat52 core promoter was active at low levels in all three species, upstream regulatory elements conserved among several pollen‐expressed genes, including the PBI element, were not functional in P. abies and P. pinaster. These results suggest that both taxa‐specific and conserved regulatory mechanisms operate to control gene expression during pollen germination and tube growth.
Seed coat structure and oxygen availability control lowtemperature germination of melon (Cucumis melo) seeds
Authors: Edelstein Menahem , Corbineau Francoise , Kigel Jaime , Nerson Haim
Published: May 2006

The involvement of the seed coat in low‐temperature germination of melon seeds was examined in two accessions differing in their ability to germinate at 14°C: Noy Yizre'el (a cold‐sensitive cultivar) and Persia 202 (a cold‐tolerant breeding line). Decoating resulted in full germination of Noy Yizre'el at 14°C, but splitting the coat increased germination only partially. Thus, the inhibition of Noy Yizre'el germination at 14°C is not due to physical constraint on radicle protrusion. At 25°C, seeds of both accessions submerged in water or agar germinated fully as long as the hilum aperture remained uncovered. Submerging the whole seed, or covering the hilum with lanolin, strongly depressed germination of Noy Yizre'el but not of Persia 202. Accessions differed in germination response to decreasing O2 concentration, with Noy Yizre'el showing higher sensitivity to hypoxia. These differences were correlated with differences in seed coat structure as well as in embryo sensitivity to hypoxia. Intercellular spaces in the outer layer of the seed coat were evident in the more tolerant Persia 202, while in the sensitive Noy Yizre'el this layer was completely sealed. Sensitivity to hypoxia increased at 15°C as compared with 25°C, the increase being greater in Noy Yizre'el. It is proposed that the seed coat‐imposed dormancy at low temperature in Noy Yizre'el is the combined result of more restricted oxygen diffusion through the seed coat and a greater embryo sensitivity to hypoxia, rather than to physical constraints of radicle break‐through or impairment of imbibition.
Tissue specific expression of cell wall proteins of seedlings of Prosopis chilensis during development and wound stress
Authors: Rodríguez José Gregorio , Cardemil Liliana
Published: May 2006

Four cell wall proteins of seedling cotyledons of Prosopis chilensis were characterized by SDS‐polyacrylamide gel electrophoresis. The molecular masses of these proteins were 180, 126, 107 and 63 kDa. All of them immuno‐crossreacted with polyclonal antibodies raised against extensin from soybean seed coats. Immuno‐dot blot analysis demonstrated that the minimum expression of cotyledonary cell wall proteins was 48 h after seed imbibition, while 24 h after wound stress the expression of these wall proteins increased four‐fold. Tissue immuno‐prints and immuno‐histochemistry showed that the proteins are expressed in the cell wall of all tissues. However, the epidermis and vascular bundles of cotyledons, hypocotyls and roots, and the living cells surrounding the wounded areas highly expressed the wall proteins. When the primary roots of the seedlings were injured by performing cuts with razor blades, the seedlings achieved a growth three times faster than control seedlings and secondary roots developed in sites close to the injuries. Immuno‐histochemistry of secondary roots revealed that the root tips and the area of the cortical tissue of the primary roots being pressed by the the emerging root tip, highly expressed the cell wall proteins.
Characteristics of Citrus cell cultures during undifferentiated growth on sucrose and somatic embryogenesis on galactose
Authors: Cabasson Cécile , Ollitrault Patrick , Côte Francois‐Xavier , Michaux‐Ferriére Nicole , Dambier Dominique , Dalnic Régine , Teisson Claude
Published: May 2006

Growth of willow‐leaf mandarin (Citrus deliciosa Ten.) nucellar callus cultures without embryo formation was supported on sucrose as the sole carbon source. Somatic embryogenesis was obtained by substituting galactose for sucrose at the same concentration (0.15 M). A histocytological study revealed proliferation of young globular embryos during the first half of the 18‐day culture cycle, irrespective of the carbon source. However, during the second half of the cycle, further embryo development failed in cell cultures on sucrose‐containing medium. The rate of cell growth and the carbohydrate depletion of the medium were 3‐fold higher on sucrose than on galactose‐containing medium. Cell suspensions on sucrose differed by an increase in calcium, phosphorus, magnesium and potassium utilization soon after subculturing, followed by a sharp decrease. Finally, the phosphorus utilization rate per g dry weight formed was 2‐fold higher in cell cultures on galactose during the second half of the culture cycle, coinciding with further embryo ontogenesis.
Changes of inositol phosphates during decapitation‐induced lateral bud break of Malus domestica
Authors: Wang Shiow Y. , Faust Miklos
Published: May 2006

An increase in phosphatidylcholine (PC), phosphatidyl‐ethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylinositol (PI) occurred during bud break induced by decapitation. Inositol‐1‐phosphate [Ins(l)P1], inositol‐1,4‐bisphosphate [Ins(1,4)P2], and inositol‐1,4,5‐triphosphate [Ins(1,4,5)P3] were found in apple buds and increased progressively following decapitation. Ins(1)P1 and Ins(1,4)P2 peaked 48 h after decapitation and Ins(1,4,5)P3 peaked 72 h after decapitation during the metabolic transition when buds emerged from dormancy. Ins(1,4)P2 and Ins(1,4,5)P3 levels declined there after. The lateral buds on shoots with intact terminals and decapitated shoots treated with indole‐3‐acetic acid (IAA) in the terminals tip remained dormant and there were no significant changes in phospholipid and inositol phosphate contents.
The contribution of fruit photosynthesis to the carbon requirement of cucumber fruits as affected by irradiance, temperature and ontogeny
Authors: Marcelis L. F. M. , Hofman‐Eijer L. R. Baan
Published: May 2006

The photosynthetic contribution of a fruit to its carbon requirement throughout ontogeny and under different growing conditions was quantified in cucumber (Cucumis sativus L. cv. Corona). In addition, the effects of shading on fruit dry matter accumulation and the diurnal course of the elongation rate were studied. Fruit darkening had no photomorphogenic effect on fruit growth, while the cumulative photosynthetic contribution of a fruit to its own carbon requirement ranged from 1 to 5%. During the day there was always a net CO2 efflux. The photosynthetic rate per fruit, calculated as the difference between rates of CO2 exchange in light and dark, increased during fruit ontogeny, while the photosynthetic rate per unit fruit surface area declined. The latter was not dependent on fruit size. The photosynthetic activity per unit surface area of fruits was estimated to be about 20–30% as efficient as that of leaves. The rate of calculated photosynthesis was reduced by 60–65% when the photosynthetically active radiation incident on the fruit decreased from 200 to 50 μmol m−2 s−1. Temperature (20–30°C) had no pronounced effect on the rate of calculated fruit photosynthesis when fruits of the same developmental stage (temperature sum) were compared. However, the relative photosynthetic contribution of a fruit to its carbon requirement increased when temperature decreased. Moreover, this contribution increased when irradiance increased or fruit growth was reduced by competing fruits. During fruit ontogeny the daily photosynthetic contribution was highest (up to 15%) in young and old fruits, with a small growth rate.
Growth and maintenance respiratory costs of cucumber fruits as affected by temperature, and ontogeny and size of the fruits
Authors: Marcelis L. F. M. , Hofman‐Eijer L. R. Baan
Published: May 2006

The rates of dry weight increase and respiration of fruits were measured throughout fruit ontogeny at 20, 25 and 30°C in cucumber (Cucumis sativus L. cv. Corona). By maintaining one or five fruits per plant, which strongly affected fruit dry weight but not ontogeny, the effects of fruit size and ontogeny on respiration could be studied separately. The respiration rate per fruit followed a sigmoid curve during fruit ontogeny, while the specific respiration rate (respiration rate per unit dry weight) declined with time after anthesis. The specific respiration rate was almost linearly related to the relative growth rate. The specific respiratory costs for both growth and maintenance were highest in young fruits, but were not affected by fruit size. The average specific respiratory costs for growth and maintenance at 25°C were 3.3–3.9 mmol CO2 g−1 and 4.0 nmol CO2 g−1 s−1, respectively. An increase in temperature had no effect on the specific respiratory costs for growth, while the costs for maintenance increased with a Q10 of about 2. The costs for growth agreed reasonably well with theoretical estimates based on the chemical composition of the fruits but not with estimates based on only the carbon and ash content. The respiratory losses as a fraction of the total carbon requirement of a fruit changed during fruit ontogeny, but were independent of temperature and were similar for slow‐ and fast‐growing fruits. The cumulative respiratory losses accounted for 13–15% of the total carbon requirement.
Comparison of carbohydrate utilization and energy charge in the yellow flag iris (Iris pseudacorus) and garden iris (Iris germanica) under anoxia
Authors: Hanhijärvi Anne M. , Fagerstedt Kurt V.
Published: May 2006

Carbohydrate and energy metabolism of the flooding‐ and anoxia‐tolerant Iris pseudacorus and the intolerant Iris germanica rhizomes were investigated under experimental anoxic conditions. Rhizomes of I. pseudacorus and I. Germanica were incubated in the absence of oxygen from 0 to 60 and 16 days, respectively. Amounts of glucose, total reducing sugars and non‐reducing sugars (starch, fructan and oligosaccharides) in the rhizomes were measured. Ethanol concentration and adenylate energy charge were determined enzymatically. Glucose content of I. pseudacorus rhizomes decreased gradually during the first 30 days under anoxia and then increased at the same time as adenylate energy charge values started to decline. In I. germanica rhizomes the changes were more dramatic and the time scale was much shorter than in I. pseudacorus but the changes were similar. Non‐reducing sugar content of I. pseudacorus rhizomes decreased rapidly during the first 15 days under oxygen deprivation and then increased again, to near starting levels at 35 days. In I. germanica the amount of non‐reducing sugars decreased gradually during the anoxic incubation. Under aerobic control conditions, adenylate energy charge (AEC) of I. pseudacorus and I. germanica rhizome tissue was 0.87±0.01 and 0.81±0.01, respectively. In I. pseudacorus AEC remained high until 30 days under anoxia. In contrast, the energy charge of I. germanica rhizome tissue remained above 0.6 for 4 days only. Large amounts of ethanol were found in anoxic rhizome tissues of I. pseudacorus (up to 0.21 M) and I. germanica (0.06 M) after 45 days and 8 days, respectively. The results are discussed in relation to flooding tolerance of these species.
Control of osmotin gene expression by ABA and osmotic stress in vegetative tissues of wild‐type and ABA‐deficient mutants of tomato
Authors: Grillo Stefania , Leone Antonella , Xu Yi , Tucci Marina , Francione Raffaella , Hasegawa Paul M. , Monti Luigi , Bressan Ray A.
Published: May 2006

Osmotin gene expression and protein synthesis were up‐regulated in young tomato (Lycopersicon esculentum cv. Rheinlands Ruhm) plants after a short exposure (24 h) to 150 mM NaCl or 100 μM abscisic acid (ABA) or after dehydration to 80% of original plant fresh weight. Osmotically induced accumulation of osmotin mRNA was accompanied by a large increase in endogenous ABA levels. Increasing accumulation of osmotin protein was also observed during a longer exposure (7 days) to salt. Upon treatment with NaCl. osmotin mRNA levels increased in both root and leaf tissues. with an additional longer transcript induced in roots. No induction of osmotin mRNA was observed upon salt or water stress of the tomato ABA‐deficient mutant sitiens. Treatment of sitiens with exogenous ABA induced osmotin mRNA accumulation to the level normally found in salt‐treated wild‐type plants. However, salt stress alone enhanced accumulation of osmotin mRNA in plants of another tomato mutant (flacca) which is also impaired in ABA synthesis. In tobacco plants carrying an osmotin promoter/β‐glucuronidase (GUS) fusion gene, NaCl induction of GUS could be only partially blocked by the ABA inhibitor fluoridone. In flacca plants simultaneous treatment with NaCl and ABA resulted in higher levels of osmotin transcript compared to those following treatment with NaCl alone. No accumulation of osmotin protein was observed after short‐ or long‐term osmotic treatments of the mutants. Our results support previous evidence that osmotin gene expression may be triggered in part through ABA and in part through a separate pathway of gene activation.
Increased chilling tolerance and altered carbon metabolism in tomato leaves following application of mechanical stress
Authors: Keller Elvira , Steffen Kenneth L.
Published: May 2006

We investigated the effects of brushing on the chilling tolerance and metabolism of nonstructural carbohydrates (soluble sugars and starch) in tomato leaves before, during and after a chilling stress. Tomato plants (Lycopersicon esculentum Mill. cv. Caruso) were cultivated either without mechanical stress application (control plants) or with daily brushing treatments for 15 days (brushed plants), prior to a 7‐day chilling treatment (8/5°C day/night). Brushing resulted in shorter plants with a 34% reduction in leaf dry weight per area and a 59% reduction of soluble sugars and starch, on a dry weight basis. The sugar to starch ratio was not affected by brushing. A greater chilling tolerance in the brushed plants was demonstrated by the maintenance of a significantly higher PSII efficiency in brushed plants (42%) compared to that of the control plants (30%) after 7 days of chilling treatment, less visible damage to the leaf tissue, and a more rapid resumption of growth during 3 days of recovery as compared to control plants. During the chilling treatment levels of soluble sugars per leaf dry weight increased 15‐fold in the brushed plants and 5‐fold in control plants. In the present study we have demonstrated that brushing can increase chilling tolerance in tomato plants. The observed differences in chilling tolerance and concentration of soluble sugars in the leaves may indicate an involvement of soluble sugar levels in acclimation to chilling.
Effects of nucleotide analogs on ATP hydrolysis by P‐type ATPases. Comparison between the canine kidney (Na++ K+) ATPase and maize root H+‐ATPase
Authors: Brauer D. , Tu S. ‐I
Published: May 2006

The mechanism by which chemical energy is converted into an electrochemical gradient by P‐type ATPase is not completely understood. The effects of ATP analogs on the canine kidney (Na++ K+) ATPase were compared to effects of the same analogs on the maize (Zea mays L. cv. W7551) root H+‐ATPase in order to identify probes for the ATP binding site of the maize root enzyme and to determine potential similarities of ATP hydrolysis mechanisms in these two enzymes. Six compounds able to modify the ATP binding site covalently were compared. These compounds could be classed into three distinct groups based on activity. The first group had little or no effect on catalytic activity of either enzyme and included 7‐chloro‐4‐nitrobenz‐2‐oxa‐1.3‐diazole. The second group, which included azido adenine analogs. fluorescein isothiocyanate and 5′‐p‐fluorosulfonylbenzoyladenine, were inhibitors of ATP hydrolysis by both enzymes. However, the sensitivity of the (Na++ K+) ATPase to inhibition was much greater than that exhibited by the maize root enzyme. The third group, which included periodate treated nucleotide derivatives and 2′,3′‐o‐(4‐benzoylbenzoyl)adenosine triphosphate. inhibited both enzymes similarly. This initial screening of these covalent modifiers indicated that 2′,3′‐o‐(4‐benzoylbenzoyl)adenosine triphosphate was the optimal covalent modifier of the ATP binding site of the maize root enzyme. Certain reagents were much more effective against the (Na++ K+) ATPase than the maize root enzyme, possibly indicating differences in the ATP binding and hydrolysis pathway for these two enzymes. Two ATP analogs that are not covalent modifiers were also tested: the trinitrophenyl derivatives of adenine nucleotides were better than 5′‐adenylylimidodiphosphate for use as an ATP binding probe.
The influence of cytokinins in nitrate regulation of nitrate reductase activity and expression in barley
Authors: Samuelson Mariann E. , Campbell Wilbur H. , Larsson Carl‐Magnus
Published: May 2006

The responses of nitrate reductase (NR) activity and levels of NR‐mRNA to environmental nitrate and exogenous cytokinins are characterised in roots and shoots of barley (Hordeum vulgare L., cv. Golf), using a chemostate‐like culture system for controlling nitrate nutrition. Experiments were mainly performed with split root cultures where nitrate‐N was supplied at a constant relative addition rate of 0.09 day−1, and distributed between the subroots in a ratio of 20%:80%. The subroot NR‐mRNA level and NR activity, as well as the endogenous level of zeatin riboside (ZR), increased when the local nitrate supply to one of the subroots was increased 4‐fold by reversing the nitrate addition ratio (i.e. from 20%:80% to 80%:20%). Also shoot levels of ZR, NR‐mRNA and NR activity increased in response to this treatment, even though the total nitrate supply remained unaltered. External supply of ZR at 0.1 μM caused an approximately 3‐fold increase in root ZR levels within 6 h. which is comparable to the nitrate‐induced increase in root ZR. External application of ZR. zeatin. isopentenyl adenine or isopentenyl adenosine at 0.1 μM caused from insignificant to 25% increases in NR‐mRNA and activity in roots and up to 100% stimulation in shoots, whereas adenine or adenosine had no effect. No synergistic effects of perturbed nitrate supply and cytokinin application were detected in either roots or shoots. The translocation of nitrate from the root to the shoot was unaffected by application of ZR or switching the nitrate distribution ratio between subroots. The data give arguments for a physiological role of cytokinins in the response of root and shoot NR to environmental nitrate availability. The nature and limitations of the physiological role of cytokinins are discussed.
CO2 assimilation, respiration and chlorophyll fluorescence in peach leaves infected by Taphrina deformans
Authors: Raggi Vittorio
Published: May 2006

Photosynthesis, respiration and chlorophyll fluorescence parameters were determined in peach (Prunus persica L. cv. Dixired) leaves naturally infected by Taphrina deformans (Berk.) Tul. and in healthy leaves (controls), in two successive springs. A drastic decrease in net photosynthesis and an evident increase in respiration in curled leaves were noted. The instantaneous PSII fluorescence yield, with no (F0) and with (F0) quenching component, and steady state fluorescence yield (under actinic light, Fs) were essentially unchanged. Maximal fluorescence in dark‐adapted (Fm) and illuminated (F′m) leaves and the corresponding variable fluorescence (Fv and Fv) clearly decreased. The indicators of PSII quantum yield (Fv/Fm) in dark‐adapted leaves, and the potential PSII excitation capture efficiency (F′v/F′m) and the quantum yield of PSII (qp [F′v/F′m]) in the light were also significantly lower in curled leaves. Decreasing tendencies were also noted for the PSII photochemical yield (photochemical quenching, qp) and in the energy status of the chloroplast (non‐photochemical quenching, qN, and Stern‐Vollmer value, NPQ) although the differences were not always significant. In curled leaves the main alteration documented is the imbalance between the drastic inhibition of CO2 fixation and the moderate decrease in photochemical reactions (i.e. Fv/Fm and ΔF/F′m), indicating changes in the energy flux.
Isolation of β‐galactosidase fractions from Japanese pear: Activity against native cell wall polysaccharides
Authors: Kitagawa Yasuhiro , Kanayama Yoshinori , Yamaki Shohei
Published: May 2006

β‐Galactosidase (EC 3.2.1.23) was purified from the cell wall of the fruit of Japanese pear (Pyrus serotina Rehder var. culta Rehder cv. Hosui) and characterized. Five peaks of β‐galactosidase activity, designated as Gal I to V, were separated by hydrophobic chromatography on butyl toyopearl and ion exchange chromatography on Mono S. These isolated β‐galactosidases were investigated with regard to their abilities to release monomeric galactose from the fractionated polymers of native cell wall (cyclo‐hexane‐trans‐1,2‐diamine tetraacetic acid‐, Na2CO3‐, guanidine thiocyanate‐ and KOH‐soluble fractions) and arabinogalactan (from larch wood). All the β‐galactosidase fractions were active against native cell wall polysaccharides although to varying degrees. Gal I reacted to all fractions of native cell wall polysaccharides although to varying degrees. Gal I reacted to all fractions of native cell wall and arabinogalactan. Gal II released much galactose only from KOH‐soluble polymers and arabinogalactan. Gal III released the most galactose. from cyclohexane‐trans‐1,2‐diamine tetraacetic acid‐, Na2CO3‐ and guanidine thiocyanate‐soluble cell wall polymers which probably contained galactosyl side chains of pectic polymers, although it did not react much to arabinogalactan. In addition, the activity of Gal Ill dramatically increased as ripening proceeded. Furthermore, Gal III was purified to homogeneity by gel filtration on TSKgel 3000SW and the size of a polypeptide was 80 kDa on SDS‐PAGE.
Chlorophyll fluorescence and photoacoustic characteristics in relationship to changes in chlorophyll and Ca2+ content of a Cu‐tolerant Silene compacta ecotype under Cu treatment
Authors: Ouzounidou Georgia , Moustakas Michael , Lannoye Robert
Published: May 2006

The effect of Cu toxicity on photosynthetic function, chlorophyll and Ca2+ content of Cu‐tolerant Silene compacta plants grown in nutrient solution was studied. Since, in plants grown under 8 μM Cu, the chlorophyll and Ca2+ concentration as well as the photosystem II (PSII) photochemistry were increased, compared to the control, the development of an adaptive mechanism of the Cu‐tolerant ecotype of S. compacta to 8 μM Cu is suggested. Increased Cu tolerance of the S. compacta ecotype reflects modulation of the photosynthetic apparatus to optimize photosynthesis. However, exposure of plants to 160 μM Cu resulted in a marked increase of the fraction of closed PSII centres and decreased quantum yield of PSII electron transport (ΦPSU) which was accompanied by a significant decline of relative quantum yield for O2 evolution (Aox/Apt). The concentration of chlorophyll and Ca2+ in leaves also decreased significantly under 160 μM Cu treatment. Photochemical quenching (qp) displayed a reduction as a result of perturbation of the photosynthetic electron transfer chain, while non‐photochemical quenching (qN) increased. High Cu treatment reduced photosynthetic productivity of S. compacta plants which can be attributed, in part, to pertubation of photosynthetic process and photosynthetic pigments as well as to Ca2+ loss.
Effect of cold exposure on cortical microtubules of rye (Secale cereale) as observed by immunocytochemistry
Authors: Pihakaski‐Maunsbach Kaarina , Puhakainen Tuula
Published: May 2006

The responses of cortical microtubules to sub‐zero temperatures were examined in non‐acclimated (NA) and cold‐acclimated (CA) rye (Secale cereale L. cv. Voima) leaf and root cells, and in protoplasts isolated enzymatically from leaves. Responses of leaf and root cells to hypertonic solutions equivalent to the dehydration response of freezing (P. L. Steponkus and D. V. Lynch 1989. J. Bioenerg. Biomembr. 21: 21–41) were also examined. At the respective growth temperatures both NA and CA leaf and root cells had typical organization and abundance of cortical microtubules as observed by indirect immunofluorescence (IIF) staining. Unchanged microtubule arrays were still present in CA leaf cells after ‐4°C treatment, while in leaf cells of NA plants and in the root cells of both NA and CA plants microtubules were shorter and less abundant. After ‐10°C treatment the cortical microtubules were almost totally depolymerized in both types of root cells and in leaf cells of NA plants, while CA leaf cells still had abundant cortical microtubule arrays. Semiquantitative analyses of cortical microtubules (MTs) of protoplasts confirmed the findings with intact leaf cells. Hypertonic treatment of NA and CA leaf cells gave similar effects as exposure of cells to sub‐zero temperatures. However, after the hypertonic treatment, more microtubules remained present in the CA root cells than in the NA root cells, suggesting that also in root cells cold acclimation increases the dehydration stability of MTs. In conclusion, cold acclimation induces both greater frost stability and greater osmotic tolerance in the cortical microtubules of the leaf cells, and greater osmotic tolerance in the microtubules of the root cells in winter rye.
The apple mitochondrial atp9 gene: RNA editing and co‐transcription with exons a and b of the nad5 gene
Authors: Kato S. , Shimamoto Y. , Mikami T.
Published: May 2006

We have isolated and characterized a transcribed segment of mitochondrial DNA (mtDNA) from apple (cv. ‘Delicious’) that contains the atp9 gene, and exons a and b of the nad5 gene. Analysis of the cDNA of the atp9 revealed 8 C to U transcript editing events resulting in 7 amino acid changes, and a new stop codon that eliminates 8 carboxy‐terminal residues, compared to the genomic sequence. The transcription patterns of atp9, and exons a and b of nad5 share RNA species, indicating that these sequences are part of the same transcriptional unit.
Alteration of gene expression in Pisum sativum tissue cultures caused by the free radical‐generating agent 2,2′‐azobis (2‐amidinopropane) dihydrochloride
Authors: Henkow Lisa , Strid Åke , Berglund Torkel , Rydström Jan , Ohlsson Anna B.
Published: May 2006

Root‐differentiated tissue cultures (PS‐R) from Pisum sativum (cv. Greenfeast) were exposed to a 5 mM solution of the free radical‐generating compound 2,2′‐azobis (2‐amidinopropane) dihydrochloride (AAPH). The levels of mRNA transcripts for two genes were examined: chs2, encoding a chalcone synthase isozyme, and cab, encoding the chlorophyll a/b‐binding protein of the light‐harvesting antenna complex. In light‐grown PS‐R, cab mRNA transcript levels decreased to 14% of controls after 6 h of exposure, whereas chs2 mRNA levels increased 50‐fold. In dark‐grown PS‐R, chs2 mRNA transcripts increased by 40‐fold compared with the controls. Glutathione determination in light‐grown PS‐R showed no substantial difference in total glutathione (GSHtot), whereas oxidized glutathione (GSSG) increased by 66% after 12 h of exposure. However, in dark‐grown PS‐R a decrease in both GSHtot and GSSG after 6 h was followed by an increase of about 70%, as compared with the controls, after 12 h of exposure. In conclusion, AAPH generated oxidative stress, reflected in changed glutathione levels and induced expression of the chs2 gene of the flavonoid biosynthetic pathway and also caused a decreased level of mRNA for the photosynthetic cab gene.
Expression of a moderately anionic peroxidase is induced by aluminum treatment in tobacco cells: Possible involvement of peroxidase isozymes in aluminum ion stress
Authors: Ezaki Bunichi , TsugUa Shinobu , Matsumoto Hideaki
Published: May 2006

To clarify the mechanism of aluminum (Al) toxicity and Al tolerance, we isolated a new clone (pAL201) from a tobacco cDNA library. Northern blot hybridization analysis indicated that the expression of pAL201 is induced by Al treatment and phosphate (P1) starvation. The complete cDNA sequence suggested that this clone encodes a moderately anionic peroxidase (EC 1.11.1.7). Analysis by isoelectric focussing indicated that a moderately anionic peroxidase (approximately pI 6.7) and two cationic peroxidases (pI 9.2 and 9.7) in the soluble fraction are activated by Al treatment and P1 starvation, while two moderately anionic isozymes are repressed by these stresses. We suppose that Al ion stress can control the activity of some peroxidase isozymes, one of which is probably induced by enhanced gene expression of pAL201. There is a possibility that some of these isozymes have some functions in Al ion stress.
The seven NAD(H)‐glutamate dehydrogenase isoenzymes exhibit similar anabolic and catabolic activities
Authors: Loulakakis Konstantinos A. , Roubelakis‐Angelakis Kalliopi A.
Published: May 2006

The specific activities of aminating NADH‐ and deaminating NAD+‐glutamate dehydrogenase (GDH, EC 1.4.1.2) varied considerably in crude extracts of grapevine (Vitis viniferaL. cv. Sultanina) callus and were dependent on the nitrogen source of the culture medium. However, dialysis of the enzyme preparations resulted in a significant decrease in the deaminating GDH specific activity while the aminating activity was not affected. The presence of malate in the crude extract resulted in erroneous overestimation of the NAD+‐GDH activity through the malate dehydrogenase reaction. Thus, in dialysed extracts, the ratio of the NADH‐GDH/NAD+‐GDH specific activities remained relatively constant irrespective of the nitrogen source. In view of this evidence, we now have modified methods for staining both the NADH‐GDH and NAD+‐GDH activities on gels in order to compare the aminating and deaminating activities of each of the 7 GDH isoenzymes. The results from the staining of NADH‐GDH and NAD+‐GDH activity of enzyme preparations from calluses revealed the same isoenzyme profile. Furthermore, separated leaf isoenzymes showed similar activity ratios and kinetic properties. These results may suggest that each one of the 7 isoenzymes have similar in vitro anabolic and catabolic activities.
Localization of ethylene biosynthesis in roots of sunflower (Helianthus annuus) seedlings
Authors: Finlayson Scott A. , Liu Jin‐Hao , Reid David M.
Published: May 2006

Sunflower (Helianthus annuus L.) seedlings were grown in aeroponic chambers which allowed for easy access to and easy harvesting of undamaged roots. In different portions of these roots we followed the rate of ethylene production, levels of 1‐aminocyclopropane‐1‐carboxylic acid (ACC), N‐malonyl‐ACC and ACC oxidase mRNA and activity of ACC oxidase. ACC oxidase was measured with an in vitro assay, ACC and N‐malonyl‐ACC by selected ion monitoring gas chromatography‐mass spectrometry. Ethylene production was highest in the tip of the root and tower in the middle and basal (part nearest the hypocotyl) portions of the root. The levels of ACC and ACC oxidase mRNA mirrored the levels of ethylene production. The lowest quantities of N‐malonyl‐ACC were found in the root tips. Upon gentle transfer of seedlings from an aeroponic system to treatment tubes, ACC content transiently increased; the greatest increase occurred in the tips. This brief rise in ACC content was not correlated with an increase in ethylene production. ACC oxidase activity was lowest in the tip and higher in the middle and base; the opposite of the pattern of ethylene production. Treating the seedlings with ACC produced a rapid rise in ACC content and ethylene production and inhibited root elongation. ACC oxidase activity was not induced by ACC treatment.
Xyloglucan endotransglycosylase activity during fruit development and ripening of apple and kiwifruit
Authors: Percy Ann E. , O'Brien Iona E. W. , Jameson Paula E. , Melton Laurence D. , MacRae ELspeth A. , Redgwell Robert J.
Published: May 2006

Xyloglucan endotransglycosylase (XET) activity was measured in apple (Malus domestica Borkh. cv. Braeburn) pericarp and kiwifruit (Actinidia deliciosa [A. Chev.] C. F. Liang et A. R. Ferguson var. deliciosa cv. Hayward) outer pericarp and core tissues in order to establish whether a correlation exists between the activity of the enzyme and different stages of fruit development Whereas the growth rate of kiwifruit paralleled changes in XET activity throughout fruit growth, that of apple did not. Both fruits showed the highest XET activity, on a fresh weight basis, in the first two weeks after anthesis when cell division was at its highest. XET activity then decreased sharply, but as the fruit increased in size (4–8 weeks after anthesis) there was a concomitant increase in XET activity in both fruits. In the latter stage of fruit development (16–26 weeks after anthesis) XET activity increased to peak at harvest in apple fruit. During this time there was relatively little increase in fruit size and presumably therefore minimal cell expansion. XET activity then declined as fruit softened after harvest. In core tissue from kiwifruit, XET activity increased throughout the later stages of fruit growth to harvest maturity in a similar manner to apple, but continued to increase after harvest until fruit were ripe. In contrast, XET activity in the outer pericarp of kiwifruit did not increase until ripening after harvest. In apple tissue up to 30% of the XET activity was cell wall bound and could not be solubilised, even in buffer containing 2 M NaCl.

The results implicate XET in cell wall assembly during cell division and expansion early in apple and kiwifruit growth. However, the disparity between apple and kiwifruit with respect to XET activity late in fruit development and ripening and the different affinities of the enzyme for the cell wall in each fruit, suggest that XET has several roles in plant development, not all of which are related to cell wall loosening during periods of accelerated growth.
Putrescine export from leaves in relation to floral transition in Sinapis alba
Authors: Havelange Andrée , Lejeune Pierre , Bernier Georges , Kaur‐Sawhney Ravindar , Galston Arthur W.
Published: May 2006

Sinapis alba L. was induced to flower by either a long day or a displaced short day. Following collection of leaf (phloem) and root (xylem) exudates from induced and non‐induced plants, polyamines in the exudates were extracted, separated and analyzed quantitatively. The titers of free and conjugated putrescine the major polyamine fractions in all samples, increased early and markedly in leaf exudates during the floral transition, coinciding closely with movement of the floral stimulus out of the induced leaf. By contrast, putrescine titer in the root exudate did not increase. A spray of difluoromethylornithine (DFMO), an irreversible inhibitor of the putrescine‐biosynthetic enzyme ornithine decarboxylase, at hour 8 of the long day considerably reduced the titer of free and conjugated putrescine in leaf exudates, and at the same time, markedly decreased the flowering response of induced plants. This effect of DFMO on flowering was substantially reversed by a simultaneous application of putrescine to the roots. DFMO sprayed on induced plants also suppressed early activation of indices of both mitosis and DNA synthesis in the shoot apical meristem. These results support the view that the extra putrescine synthesized in induced leaves is a necessary component of the floral stimulus in Sinapis.
Differential expression of β‐conglycinin genes in nodulated and non‐nodulated isolines of soybean
Authors: Ohtake Norikuni , Suzuki Momoko , Takahashi Yoshihiko , Fujiwara Toru , Chino Mitsiio , Ikarashi Taro , Ohyama Takuji
Published: May 2006

Nodulated (T202) and non‐nodulated (T201) isolines of soybean (Glycine max [L.] Merr.) were cultivated in a rotated paddy field in Niigata, Japan. The pods, and seeds were harvested at 7‐day intervals until maturity, and the subunit compositions of seed storage proteins were analyzed by SDS‐PAGE. The β‐subunit of β‐conglycinin could scarcely be detected in the non‐nodulated isoline, T201, at any period throughout seed development, although it was a major component in T202. The accumulation of α′‐ and α‐subunits of β‐conglycinin, together with the acidic and basic subunits of glycinin, appeared about one week later in seeds of T201 than in those of T202, perhaps due to a shortage of nitrogen and growth retardation. Northern hybridization could not detect the β‐subunit mRNA in immature T201 seeds, while it was pronounced in T202. These results indicate that the suppression of the β‐subunit in the non‐nodulating isoline T201 is regulated at the level of mRNA accumulation. The α′(α)‐subunit mRNAs were actively expressed in both isolines. Total nitrogen concentration was consistently lower in T201 than T202. No significant difference was observed in either the free amino acid or ureide concentrations in seeds, although the concentration of sucrose was considerably lower in T201 seeds and pods compared with T202. This result indicates the possibility that β‐subunit accunmlation was regulated not only directly by total nitrogen concentration but also by carbohydrate concentrations.

Nitrogen regulation of storage protein subunit levels of soybean seed were evaluated using T201 and T202. Greenhouse‐grown plants were subjected to different levels and timing of nitrate treatments. The culture solution (2, 5 or 10 mM NO3–was supplied from flowering, 42 days after planting (DAP), until maturation (137 DAP), or switched from 2 to 10 mM, or from 10 to 2 mM at 61 DAP. With a continuous 2 mM NO3–treatment, seed dry weight and N concentration of the T201 plants were significantly lower than those in the T202 plants due to the lack of N2 fixation by the non nodulated T201 plants. However, when adequate NO3 was supplied, N concentration and dry weight were similar in T201 and T202 seeds. When 5 mM NO3 was supplied, the subunit proportion of the seed storage protein was similar in non‐nodulating and nodulating isolines. On the other hand, when plants received a low level of NO3 (2 mM), the β‐conglycinin proportion was lower in T201 than in T2O2. Furthermore, in the nodulating T202 plants treated with 10 mM NO3–the proportion of β‐conglycinin increased markedly.

The results indicate that non‐nodulated T201 has a normal, non‐defective, β‐subunit gene and that limited N availability decreases accumulation of β‐conglycinin, whereas high N availability increases the proportion of β‐conglycinin in soybean seeds, irrespective of whether N was derived from N2 fixation or from NO3 absorption.
Effect of copper excess on the morphology of the nucleus in maize root meristem cells
Authors: Doncheva S. , Nikolov B. , Ogneva V.
Published: May 2006

Copper interferes with numerous physiological processes and can be toxic at low concentrations. We examined the effect of a 2‐week exposure to various concentrations of copper on the structure of the nucleus in maize root meristem cells by transmission electron microscopy. Copper uptake and distribution in the plants, as well as DNA synthesis were also investigated. Treatment with Cu induced alterations in the structure of the nucleus, resulting mainly in a greater density of chromatin. Morphometric analysis showed that the part of the condensed chromatin in the nucleus might be increased by Cu, an observation that was correlated with decreased DNA synthesis as measured by incorporation of 3H‐thymidine. Copper may therefore play a role in chromatin structure and one of the manifestations of Cu toxicity is an alteration in the structure of the nucleus, leading to decreased DNA synthesis.
Transfer of the Brassica tournefortii cytoplasm to B. napus for the production of cytoplasmic male sterile B. napus
Authors: Liu Ji‐Hong , Landgren Maria , Glimelius Kristina
Published: May 2006

The donor‐recipient fusion method was used to combine the cytoplasm of Brassica lournefortii with the nucleus of B. napus for the production of cytoplasmic male sterile (CMS) plants. X‐ray‐irradiated mesophyll protoplasts of B. tournefortii were fused with iodoacetamide (lOA)‐inactivated hypocotye protoplasts of B. napus. Selective conditions of IOA concentrations and X‐ray doses were determined, which resulted in recovery of fusion products and inhibition of further growth of unfused parental cells. In total, 54 plants were obtained from different fusion experiments, of which 25 were verified as cybrids or partial hybrids. Mitochondrial DNA (mtDNA) analyses using 5 mitochondrial gene probes revealed that 20 of the 25 fusion‐derived plants had mtDNA either identical, or with varying degrees of similarity, to B. lournefortii. These plants were classified into four groups on the basis of pollen viability and number. Seven plants were categorised as male sterile since they did not produce pollen or had non‐viable pollen. Of the male sterile plants, five had a mtDNA pattern identical to B. tournefortii and a nuclear DNA content corresponding to B. napus. The nuclear‐mito‐chondrial constitution of these plants thus indicates that the combination of B. tournefortii cytoplasm with the B. napus nucleus results in CMS. Furthermore, mtDNA analysis of the two additional male sterile plants which displayed a rearranged mtDNA, revealed that the only mtDNA similarity shared among all male sterile plants was specific for B. tournefortii atp6 pattern. This indicates that the atp6 region of B. tournefortii may be involved in the expression of CMS.
Regulation of the carotenoid content and chloroplast development by levulinic acid
Authors: Jilani Arshad , Kar Santosh , Bose Salil , Tripathy Baishnab C.
Published: May 2006

Chloroplast development and chlorophyll biosynthesis are co‐regulated. To understand the mechanism of regulation of chloroplast biogenesis by chlorophyll, development of the photosynthetic apparatus was monitored during greening of etiolated barley leaf discs in the presence of levulinic acid, an inhibitor of chlorophyll biosynthesis. Although not a direct inhibitor of carotenoid biosynthesis, treatment by levulinic acid resulted in a linear reduction in both chlorophyll and carotenoid contents. Chlorophyll biosynthesis appeared to control that of carotenes. In the presence of levulinic acid, photosystem II (PSII) activity decreased while photosystem I (PSI) activity increased when expressed on a chlorophyll basis. However, the activities of both photosystem I and II decreased when expressed on a per plastid basis. As expected, in the presence of low amounts of chlorophyll, the light‐harvesting chlorophyll‐protein complex II (LHCPII) was not visible in Coomassie‐stained gels in 20 mM levulinic acidtreated tissues, but was detected as a faint band by immunoblotting. This small amount of the LHCPII induced significant amounts of grana stacking, which was monitored as an increase in the ratio of variable to maximum fluorescence. When levulinic acid was washed from the leaf discs and the latter allowed to green in its absence, the chlorophyll and carotenoid contents and the photosynthetic activities approached the control values. Levulinic acid could be used to arrest the light‐induced chloroplast development at a desired phase of greening and removed by washing the leaves to restore the developmental process without any apparent toxic effect. Results demonstrate that biosynthesis of carotenes is regulated by that of chlorophylls and extremely low amounts of the LHCPII can induce grana stacking.
Ethylene production and involvement during the first steps of durum wheat (Triticum durum) anther culture
Authors: Sévenier Robert , Coumans Marc
Published: May 2006

The role of ethylene in anther culture of durum wheat (Triticum durum Desf. cv. Ardente) was analyzed by testing the effects of 2‐chloroethylphosphonic acid (ethrel) silver thiosulfate (Ag+), a‐aminooxyacetic acid (AOA) and 1‐aminocyclopropane‐l‐carboxylic acid (ACC) on microspore division observed after 21 days of culture and on development of calli estimated at day 45. The use of ethrel and Ag+ indicated a positive effect of ethylene on microspore division, whereas the use of AOA, and to a lesser extent ACC, snowed a negative effect. In contrast, the addition of ethrel or Ag+ indicated that ethylene inhibits the development of microspore‐derived calli. AOA gave contradictory results. Ethylene production by anthers was about 7 pl anther−1h−1 and decreased during culture. ACC content in the anthers was maximal at day 9, whereas malonyl ACC (MACC) increased sharply from day 0 to day 3 and then decreased. The addition of AOA or ACC to the culture medium decreased or increased, respectively, ethylene production of anthers and the ACC and/or MACC content, but at concentrations higher than those that modified the formation of calli. This formation seems to occur in two successive phases: induction and initiation of microspore division, which was promoted by ethylene, followed by callus development, which was inhibited by ethylene.
Pollen germination, tube growth and morphology, and microtubule organization after exposure to benomyl
Authors: He Yi , Palevitz Barry A. , Wetzstein Hazel Y.
Published: May 2006

The inhibitory effects of benomyl on pollen tube growth have received little attention, particularly at the microscopic and immunohistochemical levels. Pollen germination and tube growth in the presence of benomyl were evaluated in Tradescantia virginiana to investigate the effects of this fungicide on pollen germination rate, tube growth and morphology, and microtubule (Mt) organization. Benomyl was incorporated in germination media at 0,480, 600 or 720 mg 1−1. Inhibition of pollen germination, cytoplasmic streaming, and tube elongation were associated with benomyl treatments. Benomyl also induced abnormal pollen tube morphology and Mt organization. Compared to controls, Mts in the treated tubes were characteristically fewer in number, fragmented, sinuous and increasingly disorganized. At the two highest benomyl concentrations, Mts were considerably fewer or absent in apical/subapical regions of the pollen tubes. This work verifies that benomyl incorporated into germination media at concentrations lower than recommended field rates inhibit pollen germination and tube growth, and that the effects are associated with alterations of Mt organization.