bluuebunny/crossref_metadata_2025_split huggingface dataset:
The auxin responsive gene Pp‐C61 is up‐regulated in Pinus pinaster roots following inoculation with ectomycorrhizal fungi
Authors: REDDY S. M. , PANDEY A. K. , MELAYAH D. , MARMEISSE R. , GAY G. 
Published: May 2003

ABSTRACTAn indoleacetic acid (IAA) up‐regulated cDNA, referred to as Pp‐C61, was isolated by differential screening of a cDNA library constructed from auxin‐treated roots of Pinus pinaster. The Pp‐C61 cDNA contains a 1068 bp open reading frame which encodes a polypeptide sharing no homology with known proteins. The N‐terminal protein region contains a hydrophobic signal peptide suggesting that Pp‐C61 is an extracellular protein. Pp‐C61 is present as a single copy in the P. pinaster genome and homologous genes were detected in other gymnosperm and angiosperm trees. Pp‐C61 was transcriptionally regulated by auxin with a maximal mRNA accumulation 6 h after treatment. Pp‐C61 was up‐regulated by IAA concentrations as low as 10− 10m. Up‐regulation was found to be a primary (direct) response to auxin. Ethylene and abscisic acid, but not quercetin were able to promote Pp‐C61 mRNA accumulation. As a putative extracellular protein, Pp‐C61 was postulated to play a role in ectomycorrhiza formation. Pp‐C61 was up‐regulated in P. pinaster roots following inoculation with ectomycorrhizal fungi. Transcript accumulation was the highest (5.5‐fold over control) in the presence of an IAA‐overproducing mutant of Hebeloma cylindrosporum; it was less in the presence of wild‐type strains of H. cylindrosporum and Rhizopogon roseolus. Pp‐C61 transcript also accumulated upon inoculation with a non‐mycorrhizal mutant of H. cylindrosporum. These results suggest that Pp‐C61 up‐regulation corresponds to a defence reaction in response to fungal colonization.
Protein turnover in relation to maintenance metabolism at low photon flux in two marine microalgae
Authors: QUIGG A. , BEARDALL J. 
Published: May 2003

ABSTRACTAcclimation to very low photon fluxes involves adjusting a suite of physiological characteristics that collectively elicit a physiological response. Facilitating such changes is pro‐tein turnover. Dunaliella tertiolecta (Butcher) and Phaeodactylum tricornutum (Bohlin) were grown in turbidostats at a range of photon fluxes between 2 and 300 µmol photons m−2 s−1. The kinetics of pulse‐chase labelling of the protein with 3H showed that (1) two protein pools were present, one of which turned‐over rapidly (hours), and a second which turned over more slowly (days); and (2) protein turnover rates were slower in P. tricornutum than in D. tertiolecta. Phaeodactylum tricornutum had a lower maintenance coefficient for protein turnover than D. tertiolecta, and correspondingly a smaller proportion of its respiratory demands (30%) were associated with protein turnover than in D. tertiolecta (36%). There appears to be a correlation between lower metabolic activity, requiring lower protein concentrations, and an associated decreased cost of maintenance processes in P. tricornutum compared to D. tertiolecta. Differences between protein turnover rates and maintenance metabolic costs may be one of the photo‐acclimation strategies that determine which photon niches microalgae can successfully exploit.
Is stimulation of leaf photosynthesis by elevated carbon dioxide concentration maintained in the long term? A test with Lolium perenne grown for 10 years at two nitrogen fertilization levels under Free Air CO2Enrichment (FACE)
Authors: AINSWORTH E. A. , DAVEY P. A. , HYMUS G. J. , OSBORNE C. P. , ROGERS A. , BLUM H. , NÖSBERGER J. , LONG S. P. 
Published: May 2003

ABSTRACTPhotosynthesis is commonly stimulated in grasslands with experimental increases in atmospheric CO2 concentration ([CO2]), a physiological response that could significantly alter the future carbon cycle if it persists in the long term. Yet an acclimation of photosynthetic capacity suggested by theoretical models and short‐term experiments could completely remove this effect of CO2. Perennial ryegrass (Lolium perenne L. cv. Bastion) was grown under an elevated [CO2] of 600 µmol mol−1 for 10 years using Free Air CO2Enrichment (FACE), with two contrasting nitrogen levels and abrupt changes in the source : sink ratio following periodic harvests. More than 3000 measurements characterized the response of leaf photosynthesis and stomatal conductance to elevated [CO2] across each growing season for the duration of the experiment. Over the 10 years as a whole, growth at elevated [CO2] resulted in a 43% higher rate of light‐saturated leaf photosynthesis and a 36% increase in daily integral of leaf CO2 uptake. Photosynthetic stimulation was maintained despite a 30% decrease in stomatal conductance and significant decreases in both the apparent, maximum carboxylation velocity (Vc,max) and the maximum rate of electron transport (Jmax). Immediately prior to the periodic (every 4–8 weeks) cuts of the L. perenne stands, Vc,max and Jmax, were significantly lower in elevated than in ambient [CO2] in the low‐nitrogen treatment. This difference was smaller after the cut, suggesting a dependence upon the balance between the sources and sinks for carbon. In contrast with theoretical expectations and the results of shorter duration experiments, the present results provide no significant change in photosynthetic stimulation across a 10‐year period, nor greater acclimation in Vc,max and Jmax in the later years in either nitrogen treatment.
Photoprotective role of rhodoxanthin during cold acclimation in Cryptomeria japonica
Authors: HAN Q. , SHINOHARA K. , KAKUBARI Y. , MUKAI Y. 
Published: May 2003

ABSTRACTTo examine the role of rhodoxanthin in long‐term acclimation to low temperatures, we monitored seasonal changes in pigment composition, photosynthesis, chlorophyll fluorescence and the level of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) in needles of wild‐type and mutant forms of Cryptomeria japonica. In winter, rhodoxanthin accumulated in sun‐exposed needles of wild‐type plants, but not in those of the mutant. The level of chlorophyll decreased in both types of plant in winter. In contrast, the level of the xanthophyll cycle pool increased in both cases. The level of the pool in the mutant was twice that in the wild type in winter, on a Chl basis, even though the levels in both were similar in summer. The synthesis of rhodoxanthin might be triggered by photo‐inhibitory conditions, as suggested by the sustained elevated levels of zeaxanthin (Z) and antheraxanthin (A). In the wild type and the mutant, the quantum yield of CO2 fixation (φ), the photosynthetic capacity, the photochemical efficiency of photosystem II (PSII), the photochemical quenching and the level of Rubisco in summer were similar. However, all these values for the wild type were higher than those for the mutant in winter. The non‐photochemical quenching (NPQ) in the mutant in winter increased rapidly even under low light conditions due to the high sustained levels of Z and A. In contrast, in the wild type, the conversion of Z via A to rhodoxanthin prevented the rapid increase in NPQ to maintain the relatively high level of φ. These findings suggest that rhodoxanthin might play an important photoprotective role in long‐term acclimation to cold. The dynamic regulation of the amount of rhodoxanthin relative to the level of the xanthophyll cycle pool might act to maintain an appropriate balance between light absorption, photosynthesis and the thermal dissipation of energy due to excess absorbed light in winter.
Growth and water relations of Tamarix ramosissima and Populus euphratica on Taklamakan desert dunes in relation to depth to a permanent water table
Authors: GRIES D. , ZENG F. , FOETZKI A. , ARNDT S. K. , BRUELHEIDE H. , THOMAS F. M. , ZHANG X. , RUNGE M. 
Published: May 2003

ABSTRACTThe hypothesis that water relations and growth of phreatophytic Tamarix ramosissima Ledeb. and Populus euphratica Oliv. on dunes of varying height in an extremely arid Chinese desert depend on vertical distance to a permanent water table was tested. Shoot diameter growth of P. euphratica was inversely correlated with groundwater depth (GD) of 7 to 23 m (adj. R2 = 0.69, P = 0.025); growth of T. ramosissima varied independent of GD between 5 and 24 m (P = 0.385). Pre‐dawn (pd) and midday (md) water potentials were lower in T. ramosissima (minimum pd −1.25 MPa, md −3.6 MPa at 24 m GD) than in P. euphratica (minimum pd −0.9 MPa, md −3.05 MPa at 23 m GD) and did not indicate physiologically significant drought stress for either species. Midday water potentials of P. euphratica closely corresponded to GD throughout the growing season, but those of T. ramosissima did not. In both species, stomatal conductance was significantly correlated with leaf water potential (P. euphratica: adj. R2 = 0.84, P < 0.0001; T. ramosissima: adj. R2 = 0.64, P = 0.011) and with leaf‐specific hydraulic conductance (P. euphratica: adj. R2 = 0.79, P = 0.001; T. ramosissima: adj. R2 = 0.56, P = 0.019); the three variables decreased with increasing GD in P. euphratica. Stomatal conductance of P. euphratica was more strongly reduced (> 50% between −2 and −3 MPa) in response to decreasing leaf water potential than that of T. ramosissima (30% between −2 and −3 MPa). Tolerance of lower leaf water potentials due to higher concentrations of leaf osmotically active substances partially explains why leaf conductance, and probably leaf carbon gain and growth, of T. ramosissima was less severely affected by GD. Additionally, the complex below‐ground structure of large clonal T. ramosissima shrub systems probably introduces variability into the assumed relationship of xylem path length with GD.
Differential mechanisms to induce dehydration tolerance by abscisic acid and sucrose in Spathoglottis plicata (Orchidaceae) protocorms
Authors: WANG X.‐J. , LOH C.‐S. , YEOH H.‐H. , SUN W. Q. 
Published: May 2003

ABSTRACTAbscisic acid (ABA) and sucrose are known to induce dehydration tolerance of in vitro plant cells and tissues. The present study reports the presence of different mechanisms by which sucrose and ABA improve dehydration tolerance of Spathoglottis plicata (orchid) protocorms. Orchid protocorms were generated aseptically from seeds on Murashig and Skoog medium, and then treated for 7 d in medium containing 10 mg L−1 ABA and/or 10% (w/v) sucrose. Dehydration tolerance of protocorms was determined at ∼25 °C under various drying conditions at relative humidity from 7 to 93%. The actual rate of water loss (i.e. drying rate) was determined using the rate constant of tissue water loss during drying according to the first‐order kinetics. Drying rate affected dehydration tolerance. ABA treatment reduced drying rate and increased dehydration tolerance of protocorms at all relative humidity values tested. However, when compared on the basis of actual drying rates, there was no difference in dehydration tolerance between control and ABA‐treated protocorms, suggesting that ABA‐induced tolerance was correlated with the drying rate reduction. Sucrose treatment was more effective than ABA treatment for the induction of dehydration tolerance. Interestingly, sucrose only slightly affected drying rate. ABA treatment significantly enhanced the synthesis of dehydrin, whereas sucrose treatment primarily resulted in sucrose accumulation. Sucrose treatment also affected protein turnover during drying, causing a significant decrease in protein content in protocorms. Slow drying promoted the degradation of high molecular weight proteins and enhanced the synthesis of low molecular weight dehydrin. The data suggest that different physiological mechanisms are probably involved in the induction of dehydration tolerance by ABA and sucrose treatment.
Changes in mesophyll anatomy and sink–source relationships during leaf development in Quercus glauca, an evergreen tree showing delayed leaf greening
Authors: MIYAZAWA S.‐I. , MAKINO A. , TERASHIMA I. 
Published: May 2003

ABSTRACTChanges in mesophyll anatomy, gas exchange, and the amounts of nitrogen and cell wall constituents including cellulose, hemicellulose and lignin during leaf development were studied in an evergreen broad‐leaved tree, Quercus glauca, and in an annual herb, Phaseolus vulgaris. The number of chloroplasts per whole leaf in P. vulgaris increased and attained the maximal level around 10 d before full leaf area expansion (FLE), whereas it continued to increase even after FLE in Q. glauca. The increase in the number of palisade tissue cells per whole leaf continued until a few days before FLE in Q. glauca, but it had almost ceased by 10 d before FLE in P. vulgaris. The radius and height of palisade tissue cells in Q. glauca, attained their maximal levels at around FLE whereas the thickness of the mesophyll cell wall and concentrations of the cell wall constituents increased markedly after FLE. These results clearly indicated that, in Q. glauca, chloroplast development proceeded in parallel with the cell wall thickening well after completion of the mesophyll cell division and cell enlargement. The sink–source transition, defined to be the time when the increase in daily carbon exchange rate exceeds the daily increase in leaf carbon content, occurred before FLE in P. vulgaris but after FLE in Q. glauca. During leaf area expansion, the maximum daily increase in nitrogen content on a whole leaf basis (the maximum leaf areas were corrected to be identical for these species) in Q. glauca was similar to that in P. vulgaris. In Q. glauca, however, more than 70% of nitrogen in the mature leaf was invested during its sink phase, whereas in P. vulgaris it was 50%. These results suggest that Q. glauca invests nitrogen for cell division for a considerable period and for chloroplast development during the later stages. We conclude that the competition for nitrogen between cell division and chloroplast development in the area of expanding leaves can explain different greening patterns among plant species.
Gene expression associated with N‐induced shifts in resource allocation in poplar
Authors: COOKE J. E. K. , BROWN K. A. , WU R. , DAVIS J. M. 
Published: May 2003

ABSTRACTSurprisingly little is known about molecular mechanisms by which nitrogen (N) availability acts to modulate the growth of forest trees. To address this issue, differential display was used in conjunction with filter‐based arrays to identify 52 partial cDNA clones that were significantly regulated within days in response to limiting or luxuriant levels of NH4NO3 fertilization in Populus trichocarpa Torr. & Gray × deltoides Bartr. ex Marsh. A subset of these cDNAs also demonstrated shifts in expression patterns in stem‐girdled trees, a manipulative physiology technique that disrupts phloem transport. Stem girdling also induced changes in glutamine and asparagine pools which were correlated with the observed changes in expression profiles for these genes. The identity of these genes provides insight into biochemical processes that are altered by N availability in poplar. Carbon–nitrogen interactions appear to figure prominently in the N‐response. The gene expression data suggest that N availability modulates the partitioning of C and N resources into metabolic fates that have the potential to alter both wood quality and quantity, including synthesis of vegetative storage proteins, cell wall components, and terpenoids.
Growth and physiological responses of cotton (Gossypium hirsutumL.) to elevated carbon dioxide and ultraviolet‐B radiation under controlled environmental conditions
Authors: ZHAO D. , REDDY K. R. , KAKANI V. G. , READ J. J. , SULLIVAN J. H. 
Published: May 2003

ABSTRACTBetter understanding of crop responses to projected changes in climate is an important requirement. An experiment was conducted in sunlit, controlled environment chambers known as soil–plant–atmosphere–research units to determine the interactive effects of atmospheric carbon dioxide concentration [CO2] and ultraviolet‐B (UV‐B) radiation on cotton (Gossypium hirsutumL.) growth, development and leaf photosynthetic characteristics. Six treatments were used, comprising two levels of [CO2] (360 and 720 µmol mol−1) and three levels of 0 (control), 7.7 and 15.1 kJ m−2 d−1biologically effective UV‐B radiations within each CO2level. Treatments were imposed for 66 d from emergence until 3 weeks after the first flower stage. Plants grown in elevated [CO2] had greater leaf area and higher leaf photosynthesis, non‐structural carbohydrates, and total biomass than plants in ambient [CO2]. Neither dry matter partitioning among plant organs nor pigment concentrations was affected by elevated [CO2]. On the other hand, high UV‐B (15.1 kJ m−2 d−1) radiation treatment altered growth resulting in shorter stem and branch lengths and smaller leaf area. Shorter plants at high UV‐B radiation were related to internode lengths rather than the number of mainstem nodes. Fruit dry matter accumulation was most sensitive to UV‐B radiation due to fruit abscission. Even under 7.7 kJ m−2 d−1of UV‐B radiation, fruit dry weight was significantly lower than the control although total biomass and leaf photosynthesis did not differ from the control. The UV‐B radiation of 15.1 kJ m−2 d−1reduced both total (43%) and fruit (88%) dry weights due to smaller leaf area and lower leaf net photosynthesis. Elevated [CO2] did not ameliorate the adverse effects of UV‐B radiation on cotton growth and physiology, particularly the boll retention under UV‐B stress.
Enhancement of virus‐induced gene silencing through viral‐based production of inverted‐repeats
Authors: Lacomme Christophe , Hrubikova Katarina , Ingo Hein  
Published: May 2003

SummaryPlant virus‐based vectors carrying sequences homologous to endogenous genes trigger silencing through a homology‐dependent RNA degradation mechanism. This phenomenon, called virus‐induced gene silencing (VIGS), has potential as a powerful reverse‐genetics tool in functional genomic programmes through transient, loss‐of‐function screens. Here, we describe a method to enhance the robustness of the VIGS phenotype by increasing the level of dsRNA molecule production, a critical step in the VIGS response. Incorporation of 40–60 base direct inverted‐repeats into a plant viral vector generates RNA molecules that form dsRNA hairpins. A tobacco mosaic virus (TMV)‐based vector carrying such inverted‐repeats, homologous to a green fluorescent protein (gfp) transgene or an endogenous phytoene desaturase (pds) gene, generated a stronger and more pervasive VIGS phenotype than constructs carrying corresponding cDNA fragments in sense or antisense orientation. Real‐time RT‐PCR indicated that there was up to a threefold reduction in target mRNA accumulation in the tissues where VIGS was triggered by constructs carrying inverted‐repeats compared to those where it was triggered by sense or antisense constructs. Moreover, an enhanced VIGS pds phenotype was observed using a different vector, based on barley stripe mosaic virus, in the monocotyledonous host barley. This demonstrates that VIGS can be significantly improved through the inclusion of small inverted‐repeats in plant virus‐based vectors, generating a more robust loss‐of‐function phenotype. This suggests that dsRNA formation can be a limiting factor in the VIGS phenomenon.
The sfr6 mutant of Arabidopsis is defective in transcriptional activation via CBF/DREB1 and DREB2 and shows sensitivity to osmotic stress
Authors: Boyce Joy M. , Knight Heather , Deyholos Michael , Openshaw Mark R. , Galbraith David W. , Warren Gareth , Knight Marc R. 
Published: May 2003

SummaryThe sfr6 mutant of Arabidopsis displays a deficit in freezing tolerance after cold acclimation. We previously observed that the transcripts of three cold‐, ABA‐ and drought‐inducible genes, each having a C‐repeat motif or the drought‐responsive element (CRT/DRE) in its promoter, failed to normally accumulate in this mutant. We now report that the effects of sfr6 upon transcript levels are reflected in the levels of the encoded proteins, confirming that the cold‐inducible protein expression is affected by the sfr6 mutation. Using microarray analysis, we found not only that this effect may be general to cold‐inducible genes with CRT/DRE promoter elements, but also that it extends to some other genes whose promoters lack a CRT/DRE element. The role of the CRT/DRE has been empirically tested by use of a synthetic promoter, confirming that the CRT/DRE is sufficient to confer the sfr6 effect upon expression. Tolerance of osmotic stress was also found to be reduced in sfr6, consistent with a role in osmotic stress tolerance for the cold‐, ABA‐ and drought‐inducible genes whose expression is affected by the sfr6 mutation.
Genetic characterization of a pentatricopeptide repeat protein gene, orf687, that restores fertility in the cytoplasmic male‐sterile Kosena radish
Authors: Koizuka Nobuya , Imai Ritsuko , Fujimoto Hideya , Hayakawa Takahiko , Kimura Yusuke , Kohno‐Murase Junko , Sakai Takako , Kawasaki Shinji , Imamura Jun 
Published: May 2003

SummaryCytoplasmic male sterility (CMS) in plants is a maternally inherited inability to produce functional pollen, and is often associated with mitochondrial DNA abnormalities. Specific nuclear loci that suppress CMS, termed as restorers of fertility (Rf), have been identified. Previously, we identified an Rf for the CMS Kosena radish and used genetic analysis to identify the locus and create a contig covering the critical interval. To identify the Rf gene, we introduced each of the lambda and cosmid clones into the CMS Brassica napus and scored for fertility restoration. Fertility restoration was observed when one of the lambda clones was introduced into the CMS B. napus. Furthermore, introduction of a 4.7‐kb BamHI/HpaI fragment of the lambda clone is enough to restore male fertility. A cDNA strand isolated from a positive fragment contained a predicted protein (ORF687) of 687 amino acids comprising 16 repeats of the 35‐amino acid pentatricopeptide repeat (PPR) motif. Kosena CMS radish plants were found to express an allele of this gene possessing four substituted amino acids in the second and third repeats of the PPR suggesting that the domains formed by these repeats in ORF687 are essential for fertility restoration. Protein levels of the Kosena CMS‐associated mitochondrial protein ORF125 were considerably reduced in plants in which fertility was restored, although mRNA expression was normal. Regarding the possible role for PPR‐containing proteins in the regulation of the mitochondrial gene, we propose that ORF687 functions either directly or indirectly to lower the levels of ORF125, resulting in the restoration of fertility in CMS plants.
Ku80‐ and DNA ligase IV‐deficient plants are sensitive to ionizing radiation and defective in T‐DNA integration
Authors: Friesner Joanna , Britt Anne B. 
Published: May 2003

SummaryDouble‐strand break (DSB) repair pathways catalyze the rejoining of broken chromosomes and the integration of transforming DNAs. These processes have been well characterized in bacteria, fungi, and animals. Plants are generally thought primarily to utilize a non‐homologous end joining (NHEJ) pathway to repair DSBs and integrate transgenes, as transforming DNAs with large tracts of homology to the chromosome are integrated at random. In order to test the hypothesis that NHEJ is an important pathway for the repair of DSBs in plants, we isolated T‐DNA insertion mutations in the Arabidopsis homologs of the Ku80 and DNA ligase IV genes, required for the initiation and completion, respectively, of NHEJ. Both mutants were hypersensitive to the cytostatic effects of gamma radiation, suggesting that NHEJ is indeed a critical pathway for the repair of DSBs. T‐DNA insertion rates were also decreased in the mutants, indicating that Ku80 and DNA ligase IV play an important role in either the mechanism or the regulation of T‐DNA integration in Arabidopsis.