The study of the interaction between ABA and sugar on the leaf starch degradation in Arabidopsis thaliana

• Main Authors: Yi-Zhou Zeng, 曾翊洲
• Other Authors: Wen-Luan Wu
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/99113812960135188020

碩士 === 國立成功大學 === 生命科學系碩博士班 === 94 === 　　Starch, composed of glucose residues exclusively, is the major storage carbohydrate in higher plants. Transitory starch accumulates in chloroplasts during the day and is degraded at night. Up to date, there is little known about the regulation of transitory starch metabolism. Sugar is essential to plant growth, however, high sugar levels resulted in a constraint on plant growth and starch degradation. The accumulation of starch was accompanied by induction at the expression of a starch biosynthesis gene, ApL3 (AGPase large subunit 3). Recent studies demonstrated that sugar signaling was tightly coupled with phytohormone abscisic acid (ABA). Although ABA is well known in stress adaptation, the role of ABA in starch degradation was remains to be elucidated. In this study, we investigated the interaction between ABA and sugar on starch metabolism in Arabidopsis. In the presence of high sugar levels, wild-type seedlings exhibited the shorter root and starch-excess phenotypes. These results revealed that high sugar levels had negative effects on root elongation and starch degradation. In contrast, exogenous ABA inhibited root elongation but promoted starch degradation, suggesting that ABA had a positive role in the inhibition of root growth and starch degradation. In addition, exogenous ABA was resistant to the high sugar levels, suggesting that the antagonistic interaction between high sugar levels and ABA. RT-PCR analysis showed that the starch degradation-related gene, SEX1 (STARCH EXCESS 1), was induced by ABA and the starch contents of sex1 mutant were not affected by ABA, revealing that SEX1 was necessary for ABA-mediated starch degradation. In summary, ABA has the antagonistic affect on sugar-induced starch accumulation and SEX1 is essential for ABA-mediated starch degradation.