淀粉合酶IIa突变或变异对大麦、小麦和水稻胚乳直链淀粉含量的不同影响，取决于淀粉合酶I和淀粉分支酶IIb在淀粉颗粒和造粉体基质之间的分布。

The different effects of starch synthase IIa mutations or variation on endosperm amylose content of barley, wheat and rice are determined by the distribution of starch synthase I and starch branching enzyme IIb between the starch granule and amyloplast stroma.

作者信息

Luo Jixun, Ahmed Regina, Kosar-Hashemi Behjat, Larroque Oscar, Butardo Vito M, Tanner Greg J, Colgrave Michelle L, Upadhyaya Narayana M, Tetlow Ian J, Emes Michael J, Millar Anthony, Jobling Stephen A, Morell Matthew K, Li Zhongyi

机构信息

CSIRO Agriculture Flagship, GPO Box 1600, Canberra, ACT, 2601, Australia.

出版信息

Theor Appl Genet. 2015 Jul;128(7):1407-19. doi: 10.1007/s00122-015-2515-z. Epub 2015 Apr 19.

DOI:10.1007/s00122-015-2515-z

Abstract

The distribution of starch synthase I and starch branching enzyme IIb between the starch granule and amyloplast stroma plays an important role in determining endosperm amylose content of cereal grains. Starch synthase IIa (SSIIa) catalyses the polymerisation of intermediate length glucan chains of amylopectin in the endosperm of cereals. Mutations of SSIIa genes in barley and wheat and inactive SSIIa variant in rice induce similar effects on the starch structure and the amylose content, but the severity of the phenotypes is different. This study compared the levels of transcripts and partitioning of proteins of starch synthase I (SSI) and starch branching enzyme IIb (SBEIIb) inside and outside the starch granules in the developing endosperms of these ssIIa mutants and inactive SSIIa variant. Pleiotropic effects on starch granule-bound proteins suggested that the different effects of SSIIa mutations on endosperm amylose content of barley, wheat and rice are determined by the distribution of SSI and SBEIIb between the starch granule and amyloplast stroma in cereals. Regulation of starch synthesis in ssIIa mutants and inactive SSIIa variant may be at post-translational level or the altered amylopectin structure deprives the affinity of SSI and SBEIIb to amylopectin.

摘要

淀粉合酶I和淀粉分支酶IIb在淀粉颗粒与造粉体基质之间的分布，在决定谷物胚乳直链淀粉含量方面起着重要作用。淀粉合酶IIa（SSIIa）催化谷物胚乳中支链淀粉中等长度葡聚糖链的聚合。大麦和小麦中SSIIa基因的突变以及水稻中无活性的SSIIa变体，对淀粉结构和直链淀粉含量产生相似的影响，但表型的严重程度有所不同。本研究比较了这些ssIIa突变体和无活性SSIIa变体发育中的胚乳淀粉颗粒内外淀粉合酶I（SSI）和淀粉分支酶IIb（SBEIIb）的转录水平和蛋白质分配情况。对淀粉颗粒结合蛋白的多效性影响表明，SSIIa突变对大麦、小麦和水稻胚乳直链淀粉含量的不同影响，是由谷物中淀粉颗粒与造粉体基质之间SSI和SBEIIb的分布决定的。ssIIa突变体和无活性SSIIa变体中淀粉合成的调控可能处于翻译后水平，或者支链淀粉结构的改变剥夺了SSI和SBEIIb对支链淀粉的亲和力。