A mutant of Arabidopsis lacking a chloroplastic isoamylase accumulates both starch and phytoglycogen

被引:183
作者
Zeeman, SC
Umemoto, T
Lue, WL
Au-Yeung, P
Martin, C
Smith, AM
Chen, J
机构
[1] John Innes Ctr Plant Sci Res, Norwich NR4 7UH, Norfolk, England
[2] Acad Sinica, Inst Mol Biol, Taipei, Taiwan
关键词
D O I
10.1105/tpc.10.10.1699
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
In this study, our goal was to evaluate the role of starch debranching enzymes in the determination of the structure of amylopectin. We screened mutant populations of Arabidopsis for plants with alterations in the structure of leaf starch by using iodine staining. The leaves of two mutant lines stained reddish brown, whereas wild-type leaves stained brownish black, indicating that a more highly branched polyglucan than amylopectin was present. The mutants were allelic, and the mutation mapped to position 18.8 on chromosome 1. One mutant line lacked the transcript for a gene with sequence similarity to higher plant debranching enzymes, and both mutants lacked a chloroplastic starch-hydrolyzing enzyme. This enzyme was identified as a debranching enzyme of the isoamylase type. The loss of this isoamylase resulted in a 90% reduction in the accumulation of starch in this mutant line when compared with the wild type and in the accumulation of the highly branched water-soluble polysaccharide phytoglycogen. Both normal starch and phytoglycogen accumulated simultaneously in the same chloroplasts in the mutant lines, suggesting that isoamylase has an indirect rather than a direct role in determining amylopectin structure.
引用
收藏
页码:1699 / 1711
页数:13
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