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Analysis of Arabidopsis thaliana mutants affected in water deficit tolerance

Anne Plessis
Abstract : Abscisic acid (ABA) is crucial for plant water deficit tolerance. Its accumulation rapidly stimulates stomatal closure thus limiting water loss and induces the expression of genes involved in cellular protection and detoxification. Infrared thermography allows real-time observation of temperature differences between « cold » plants with open stomata and « hot » plants with closed stomata. In order to identify new genes involved in the response to water deficit, this technique had been used in an ABA-deficient mutant aba3-1 « hot » suppressor screen in Arabidopsis thaliana. Four « hot » recessive suppressor mutants, named has aba3- 1 (hot ABA-deficient suppressors), more resistant than aba3-1 to a progressive dehydration had been isolated and were studied. ABA measurements showed that their phenotypes were not explained by increased ABA accumulation. Their biometric, water and biotic stress responses were examined as well as ABA-sensitivity in several tissues. In addition, microarray analysis of non-stressed leaf expression profiles was carried out. The has mutations have been selected without the aba3-1 mutation and some phenotypes have been examined in this wild-type background. The has1 mutation seems complex, causing the disruption of a gene coding for a putative RNA helicase, the mutation of which does not explain all of the has1 aba3-1 phenotypes. The has2 mutation decreases water loss on both rapid and prolonged water deficit in both wild-type and aba3-1 contexts. Transcriptome analyses showed that gene expression in the has2 aba3-1 mutant is close to that of wild-type in agreement with the suppression of aba3-1 sensitivity to water deficit. The has3 mutation seems to induce ABA hypersensitivity in stomata and seeds. Finally, has4 aba3-1 has modified ABA sensitivity in all tissues tested and has the strongest suppression of water deficit phenotype of the four suppressors ; these seem to be conserved in has4 . Based on these characteristics, this locus was selected in priority for mapping. The analysis of the 32 genes within the mapping interval is well underway and the mutated gene should be identified soon. has2 and has3 loci mapping has identified intervals of 0.5 and 1 Mb respectively. The four has loci are distinct and their mapping regions do not contain any previous studied gene in which a mutation would match their phenotypes. This project should lead to the identification of at least three new genes involved into water deficit tolerance.
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Submitted on : Tuesday, April 14, 2009 - 8:00:00 AM
Last modification on : Tuesday, April 14, 2009 - 8:00:00 AM
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Anne Plessis. Analysis of Arabidopsis thaliana mutants affected in water deficit tolerance. Life Sciences [q-bio]. AgroParisTech, 2008. English. ⟨NNT : 2008AGPT0102⟩. ⟨pastel-00004813⟩

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