Biochemical and genetic analysis of the effects of amylose-extender mutation in rice endosperm
Biochemical and genetic analysis of the effects of amylose-extender mutation in rice endosperm
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DOI：
10.1104/pp.127.2.459
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发表时间：
2001-10-01
期刊：
影响因子：
7.4
通讯作者：
Satoh, H
中科院分区：
文献类型：
--
作者：
Nishi, A;Nakamura, Y;Satoh, H
对水稻直链淀粉延伸器(Ae)突变体的生化分析表明，淀粉分支酶IIb(BEIIb)基因突变通过减少聚合度为17或更低的短链来特异性地改变胚乳支链淀粉的结构，其中聚合度为8~12的短链减少的幅度最大。这种变化的程度与淀粉颗粒在尿素溶液中的糊化特性有关。Ae突变导致BEIIb活性显著降低。Ae突变体的可溶性淀粉合成酶I(SSI)活性显著低于野生型，表明该突变对SSI活性具有多效性。BEI、BEIIa、ADP-Glc焦磷酸化酶、异淀粉酶、异淀粉酶、普鲁兰酶和蔗糖合成酶的活性不受该突变的影响。因此，BEIIb的功能不能被Ela和BEL所补充。这些结果有力地表明BEIIb在短链的转移中起着特定的作用，这些短链可能被SS延伸，形成水稻胚乳支链淀粉簇的A链和B-1链。
Biochemical analysis of amylose-extender (ae) mutant of rice (Oryza saliva) revealed that the mutation in the gene for starch-branching enzyme IIb (BEIIb) specifically altered the structure of amylopectin in the endosperm by reducing short chains with degree of polymerization of 17 or less, with the greatest decrease in chains with degree of polymerization of 8 to 12. The extent of such change was correlated with the gelatinization properties of the starch granules, as determined in terms of solubility in urea solution. The ae mutation caused a dramatic reduction in the activity of BEIIb. The activity of soluble starch synthase I (SSI) in the ae mutant was significantly lower than in the wild type, suggesting that the mutation had a pleiotropic effect on the SSI activity. In contrast, the activities of BEI, BEIIa, ADP-Glc pyrophosphorylase, isoamylase, isoamylase, pullulanase, and Suc synthase were not affected by the mutation. Therefore, it is stressed that the function of BEIIb cannot be complemented by Ella and BEL These results strongly suggest that BEIIb plays a specific role in the transfer of short chains, which might then be extended by SS to form the A and B-1 chains of amylopectin cluster in rice endosperm.