摘要 :
Les lignines sont des polymères phénoliques spécifiques des plantes supérieures terrestres Elles imperméabilisent les vaisseaux et rigidifient les fibres. Leur biosynthèse est complexe et nécessite de nombreuses étapes. La...
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Les lignines sont des polymères phénoliques spécifiques des plantes supérieures terrestres Elles imperméabilisent les vaisseaux et rigidifient les fibres. Leur biosynthèse est complexe et nécessite de nombreuses étapes. La biosynthèse des monolignols, les précurseurs de ces polymères, comprend de nombreuses étapes de réduction, d'hydroxylation et de méthylation. L'utilisation d'Arabidopsis permet de disposer de mutants pour chacune de ces étapes et de déterminer l'impact du blocage d'une étape particulière sur les caractéristiques des lignines et les propriétés des parois lignifiées. Les résultats peuvent être extrapolés à des espèces annuelles d'intérêt agronomique, comme le mais et la luzerne, ou à des espèces forestières, comme le peuplier et l'eucalyptus, dans le but d'améliorer leur production et leurs usages.
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Several recent proteomic studies of plant peroxisomes indicate that the peroxisomal matrix harbors multiple ATPdependent
enzymes and chaperones. However, it is unknown whether plant peroxisomes are able to produce ATP by
substrate...
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Several recent proteomic studies of plant peroxisomes indicate that the peroxisomal matrix harbors multiple ATPdependent
enzymes and chaperones. However, it is unknown whether plant peroxisomes are able to produce ATP by
substrate-level phosphorylation or whether external ATP fuels the energy-dependent reactions within peroxisomes. The
existence of transport proteins that supply plant peroxisomes with energy for fatty acid oxidation and other ATP-dependent
processes has not previously been demonstrated. Here, we describe two Arabidopsis thaliana genes that encode
peroxisomal adenine nucleotide carriers, PNC1 and PNC2. Both proteins, when fused to enhanced yellow fluorescent
protein, are targeted to peroxisomes. Complementation of a yeast mutant deficient in peroxisomal ATP import and in vitro
transport assays using recombinant transporter proteins revealed that PNC1 and PNC2 catalyze the counterexchange of
ATP with ADP or AMP. Transgenic Arabidopsis lines repressing both PNC genes were generated using ethanol-inducible
RNA interference. A detailed analysis of these plants showed that an impaired peroxisomal ATP import inhibits fatty acid
breakdown during early seedling growth and other b-oxidation reactions, such as auxin biosynthesis. We show conclusively
that PNC1 and PNC2 are essential for supplying peroxisomes with ATP, indicating that no other ATP generating systems
exist inside plant peroxisomes.
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摘要 :
У проростков Arabidopsis thaliana местной популяции и экотипа Landsberg erecta проведен сравнительный анализ изменений S3 количественных ульт...
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У проростков Arabidopsis thaliana местной популяции и экотипа Landsberg erecta проведен сравнительный анализ изменений S3 количественных ультраструктурных признаков клеток и их компонентов в апексе побега в связи с заложением и начальным ростом листьев. Эти признаки включали парциальный объем на клетку 12 клеточных компонентов, их линейные размеры — 7, частоту встречаемости — 6 и 21 параметр структуры пластид и митохондрий. По этим данным были рассчитаны индивидуальный объем и число на клетку ядрышек, пластид, митохондрий, пероксисом, диктиосом и вакуолей, объем ядер, а также число на клетку цитоплазматических рибосом. Кроме этого, рассчитаны площадь поверхности внутренних мембран митохондрий и тилакоидов пластид, объем и число на пластиду и клетку пластоглобул, тилакоидов, гран, крахмальных зерен. Установлено, в частности, что внутренние клетки периферической зоны апикальной меристемы проростков местной популяции на стадии заложения 4-го листа, имеющие объем 143 мкм~3, содержат в среднем 12 пластид, 52 митохондрии, 2 очень мелких (0.02 мкм~3) пероксисомы, 10 диктиосом и 51 мелкую (по 0.05 мкм~3) вакуоль. При заложении листа значения всех исследованных параметров клеток достоверно не изменяются. Первые признаки дифференциации — увеличение размера и парциального объема пластид — выявляются в примордиях длиной 70 мкм. На следующей стадии изменяются уже более 10 признаков, и не только пластид, но и других органелл.
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The Arabidopsis thaliana histone H2A gene HTA1 is essential for efficient transformation of Arabidopsis roots by Agrobacterium
tumefaciens. Disruption of this gene in the rat5 mutant results in decreased transformation. In Arabido...
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The Arabidopsis thaliana histone H2A gene HTA1 is essential for efficient transformation of Arabidopsis roots by Agrobacterium
tumefaciens. Disruption of this gene in the rat5 mutant results in decreased transformation. In Arabidopsis, histone
H2A proteins are encoded by a 13-member gene family. RNA encoded by these genes accumulates to differing levels in roots
and whole plants; HTA1 transcripts accumulate to levels up to 1000-fold lower than do transcripts of other HTA genes. We
examined the extent to which other HTA genes or cDNAs could compensate for loss of HTA1 activity when overexpressed in
rat5 mutant plants. Overexpression of all tested HTAcDNAs restored transformation competence to the rat5 mutant. However,
only the HTA1 gene, but not other HTA genes, could phenotypically complement rat5 mutant plants when expressed from their
native promoters. Expression analysis ofHTApromoters indicated that they had distinct but somewhat overlapping patterns of
expression in mature plants. However, only the HTA1promoter was induced by wounding or by Agrobacterium infection of root
segments. Our data suggest that, with respect to Agrobacterium-mediated transformation, all tested histone H2A proteins are
functionally redundant. However, this functional redundancy is not normally evidenced because of the different expression
patterns of the HTA genes.
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摘要 :
Arabidopsis thaliana GAMT1 and GAMT2 encode enzymes that catalyze formation of the methyl esters of gibberellins (GAs).
Ectopic expression of GAMT1 or GAMT2 in Arabidopsis, tobacco (Nicotiana tabacum), and petunia (Petunia hybrida...
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Arabidopsis thaliana GAMT1 and GAMT2 encode enzymes that catalyze formation of the methyl esters of gibberellins (GAs).
Ectopic expression of GAMT1 or GAMT2 in Arabidopsis, tobacco (Nicotiana tabacum), and petunia (Petunia hybrida)
resulted in plants with GA deficiency and typical GA deficiency phenotypes, such as dwarfism and reduced fertility. GAMT1
and GAMT2 are both expressed mainly in whole siliques (including seeds), with peak transcript levels from the middle until
the end of silique development. Within whole siliques, GAMT2 was previously shown to be expressed mostly in developing
seeds, and we show here that GAMT1 expression is also localized mostly to seed, suggesting a role in seed development.
Siliques of null single GAMT1 and GAMT2 mutants accumulated high levels of various GAs, with particularly high levels of
GA1 in the double mutant. Methylated GAs were not detected in wild-type siliques, suggesting that methylation of GAs by
GAMT1 and GAMT2 serves to deactivate GAs and initiate their degradation as the seeds mature. Seeds of homozygous
GAMT1 and GAMT2 null mutants showed reduced inhibition of germination, compared with the wild type, when placed on
plates containing the GA biosynthesis inhibitor ancymidol, with the double mutant showing the least inhibition. These
results suggest that the mature mutant seeds contained higher levels of active GAs than wild-type seeds.
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Within the Arabidopsis thaliana family of 21 heat stress transcription factors (Hsfs), HsfA9 is exclusively expressed in late
stages of seed development. Here, we present evidence that developmental expression of HsfA9 is regulate...
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Within the Arabidopsis thaliana family of 21 heat stress transcription factors (Hsfs), HsfA9 is exclusively expressed in late
stages of seed development. Here, we present evidence that developmental expression of HsfA9 is regulated by the seedspecific
transcription factor ABSCISIC ACID–INSENSITIVE3 (ABI3). Intriguingly, ABI3 knockout lines lack detectable levels of
HsfA9 transcript and protein, and further ectopic expression of ABI3 conferred the ability to accumulate HsfA9 in response
to abscisic acid in transgenic plantlets. Consequently, the most abundant heat stress proteins (Hsps) in seeds (Hsp17.4-CI,
Hsp17.7-CII, and Hsp101) were not detectable in the ABI3 knockout lines, but their expression could be detected in plants
ectopically expressing HsfA9 in vegetative tissues. Furthermore, this seed-specific transcription factor cascade was
reconstructed in transient b-glucuronidase reporter assays in mesophyll protoplasts by showing that ABI3 could activate
the HsfA9 promoter, whereas HsfA9 in turn was shown to be a potent activator on the promoters of Hsp genes. Thus, our
study establishes a genetic framework in which HsfA9 operates as a specialized Hsf for the developmental expression of
Hsp genes during seed maturation.
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摘要 :
Белок СОР1 (от constitutive chotomorphogenesis 1) является ключевым регулятором фотоморфогенеза растений. В темноте СОР1 влияет на экспрессию...
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Белок СОР1 (от constitutive chotomorphogenesis 1) является ключевым регулятором фотоморфогенеза растений. В темноте СОР1 влияет на экспрессию более 20% генов Arabidopsis thaliana, и в первую очередь это связано с участием СОР1 в протеолизе светорегулируемьгх транскрипционных факторов, и подавляет экспрессию генов фотоморфогенеза. Особенности регуляции позволяют СОР1 контролировать разные стадии развития растений. СОР1 проявляет активность ЕЗ убиквитинлига-зы и одновременно принимает участие в регуляции транскрипции УФ-В чувствительных генов. В настоящем обзоре проанализированы современные представления о механизмах действия СОР1.
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摘要 :
Sulfur is a macronutrient that is necessary for plant growth and development. Sulfate, a major source of sulfur, is taken up by plant roots and transported into various tissues for assimilation. During sulfate limitation, expressi...
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Sulfur is a macronutrient that is necessary for plant growth and development. Sulfate, a major source of sulfur, is taken up by plant roots and transported into various tissues for assimilation. During sulfate limitation, expression of miR395 is significantly up-regulated. miR395 targets two families of genes, ATP sulfurylases (encoded by APS genes) and sulfate transporter 2;1 (SULTR2;1, also called AST68), both of which are involved in the sulfate metabolism pathway. Their transcripts are suppressed strongly in miR395-over-expressing transgenic Arabidopsis, which over-accumulates sulfate in the shoot but not in the root. APS1 knockdown mutants accumulate twice as much sulfate as the wild-type. By constructing APS4-RNAi transgenic plants, we found that silencing the APS4 gene also results in over-accumulation of sulfate. Even though miR395-over-expressing transgenic plants over-accumulate sulfate in the shoot, they display sulfur deficiency symptoms. Additionally, the distribution of sulfate from older to younger leaves is impaired in miR395-over-expressing plants, similar to a SULTR2;1 loss-of-function mutant. The aps1-1 sultr2;1 APS4-RNAi triply repressed mutants phenocopied miR395-over-expressing plants. Our research showed that miR395 is involved in the regulation of sulfate accumulation and allocation by targeting APS genes and SULTR2;1, respectively.
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摘要 :
Sulfur is a macronutrient that is necessary for plant growth and development. Sulfate, a major source of sulfur, is taken up by plant roots and transported into various tissues for assimilation. During sulfate limitation, expressi...
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Sulfur is a macronutrient that is necessary for plant growth and development. Sulfate, a major source of sulfur, is taken up by plant roots and transported into various tissues for assimilation. During sulfate limitation, expression of miR395 is significantly up-regulated. miR395 targets two families of genes, ATP sulfurylases (encoded by APS genes) and sulfate transporter 2;1 (SULTR2;1, also called AST68), both of which are involved in the sulfate metabolism pathway. Their transcripts are suppressed strongly in miR395-over-expressing transgenic Arabidopsis, which over-accumulates sulfate in the shoot but not in the root. APS1 knockdown mutants accumulate twice as much sulfate as the wild-type. By constructing APS4-RNAi transgenic plants, we found that silencing the APS4 gene also results in over-accumulation of sulfate. Even though miR395-over-expressing transgenic plants over-accumulate sulfate in the shoot, they display sulfur deficiency symptoms. Additionally, the distribution of sulfate from older to younger leaves is impaired in miR395-over-expressing plants, similar to a SULTR2;1 loss-of-function mutant. The aps1-1 sultr2;1 APS4-RNAi triply repressed mutants phenocopied miR395-over-expressing plants. Our research showed that miR395 is involved in the regulation of sulfate accumulation and allocation by targeting APS genes and SULTR2;1, respectively.
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摘要 :
In Arabidopsis, SULTR1;1 and SULTR1;2 are two genes proposed to be involved in high-affinity sulphate uptake from the soil solution. We address here the specific issue of their functional redundancy for the uptake of sulphate and ...
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In Arabidopsis, SULTR1;1 and SULTR1;2 are two genes proposed to be involved in high-affinity sulphate uptake from the soil solution. We address here the specific issue of their functional redundancy for the uptake of sulphate and for the accumulation of its toxic analogue selenate with regard to plant growth and selenate tolerance. Using the complete set of genotypes, including the wild-type, each one of the single sultr1;1 and sultr1;2 mutants and the resulting double sultr1;1-sultr1;2 mutant, we performed a detailed phenotypic analysis of root length, shoot biomass, sulphate uptake, sulphate and selenate accumulation and selenate tolerance. The results all ordered the four different genotypes according to the same functional hierarchy. Wild-type and sultr1;1 mutant plants displayed similar phenotypes. By contrast, sultr1;1-sultr1;2 double-mutant plants showed the most extreme phenotype and the sultr1;2 mutant displayed intermediate performances. Additionally, the degree of selenate tolerance was directly related to the seedling selenate content according to a single sigmoid regression curve common to all the genotypes. The SULTR1;1 and SULTR1;2 genes display unequal functional redundancy, which leaves open for SULTR1;1 the possibility of displaying an additional function besides its role in sulphate membrane transport.
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