Journal Article

Characterization of an <i>Arabidopsis thaliana</i> Mutant that Has a Defect in ABA Accumulation: ABA-Dependent and ABA-Independent Accumulation of Free Amino Acids during Dehydration

Eiji Nambara, Hiroshi Kawaide, Yuji Kamiya and Satoshi Naito

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 39, issue 8, pages 853-858
Published in print August 1998 | ISSN: 0032-0781
Published online August 1998 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029444
Characterization of an Arabidopsis thaliana Mutant that Has a Defect in ABA Accumulation: ABA-Dependent and ABA-Independent Accumulation of Free Amino Acids during Dehydration

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In an attempt to elucidate the physiological role of ABA in seed dormancy and the adaptive response to dehydration, we isolated an ABA-deficient mutant of Arabidopsis thaliana (L.) Heynh. which germinated in the presence of a gibberellin biosynthetic inhibitor. Genetic analysis showed this mutation is a new allele of a recently reported locus aba2, and therefore has been designated aba2-2. The levels of endogenous ABA in fresh and dehydrated tissues of the aba2-2 mutant were highly reduced compared to those of wild-type plants. As a consequence, aba2-2 plants wilt and produce seeds with reduced dormancy. Dark germinated seedlings of the aba2-2 mutant showed true leaves, which were not observed in those of the wild type, indicating that abal-2 em bryos grew precociously during seed maturation. In the dehydrated tissues of the wild-type plants, the levels of free proline, isoleucine and leucine were elevated to a content approximately 100-fold higher than those in fresh tissues. In contrast to the wild-type plants, dehydration-induced accumulation of proline was highly suppressed in the aba2-2 mutant plants while that of leucine and isoleucine accumulated. Furthermore, exogenous application of ABA to wild-type plants promoted accumulation of free proline, but not leucine nor isoleucine. These results suggest that dehydration-induced accumulation of free leucine and isoleucine is achieved independent of ABA.

Keywords: ABA; Arabidopsis; Branched-chain amino acids; Dehydration

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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