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The defective effect of starch branching enzyme IIb from weak to strong induces the formation of biphasic starch granules in amylose-extender maize endosperm.
Plant Molecular Biology ( IF 5.1 ) Pub Date : 2020-03-19 , DOI: 10.1007/s11103-020-00998-w
Wei He 1, 2 , Xiangguo Liu 3 , Lingshang Lin 1, 2 , Ahui Xu 1, 2 , Dongyun Hao 3 , Cunxu Wei 1, 2
Affiliation  

Biphasic starch granules in maize ae mutant underwent the weak to strong SBEIIb-defective effect during endosperm development, leading to no birefringence in their exterior due to extended long branch-chains of amylopectin. Biphasic starch granules are usually detected regionally in cereal endosperm lacking starch branching enzyme (SBE). However, their molecular structure, formation mechanism, and regional distribution are unclear. In this research, biphasic starch granules were observed in the inner region of crown endosperm of maize ae mutant, and had poorly oriented structure with comb-like profiles in their exterior. The inner endosperm (IE) rich in biphasic starch granules and outer endosperm (OE) without biphasic starch granules were investigated. The starch had lower amylose content and higher proportion of long branch-chains of amylopectin in IE than in OE, and the exterior of biphasic starch granules had less amylose and more long branch-chains of amylopectin than the interior. Compared with OE, the expression pattern of starch synthesis related enzymes changed significantly in IE. The granule-bound starch synthase I activity within biphasic starch granules decreased slightly. The IE experienced more severe hypoxic stress than OE, and the up-regulated anaerobic respiration pathway indicated an increase in carbon consumption. The starch in IE underwent the SBEIIb-defective effect from weak to strong due to the lack of sufficient carbon inflow, leading to the formation of biphasic starch granules and their regional distribution in endosperm. The results provided information for understanding the biphasic starch granules.

中文翻译:

淀粉支化酶IIb的缺陷作用由弱到强诱导直链淀粉玉米胚乳中双相淀粉颗粒的形成。

玉米ae突变体中的双相淀粉颗粒在胚乳发育过程中经历了从弱到强的SBEIIb缺陷效应,由于支链淀粉的长支链延长,导致它们的外部没有双折射。双相淀粉颗粒通常在缺乏淀粉支化酶 (SBE) 的谷物胚乳中局部检测到。然而,它们的分子结构、形成机制和区域分布尚不清楚。在本研究中,在玉米ae突变体冠胚乳内部区域观察到双相淀粉颗粒,其结构定向不良,外部呈梳状轮廓。研究了富含双相淀粉颗粒的内胚乳(IE)和不含双相淀粉颗粒的外胚乳(OE)。与OE相比,IE中的淀粉直链淀粉含量较低,支链淀粉长支链的比例较高,而双相淀粉颗粒外部的直链淀粉含量低于内部,支链淀粉长支链的比例高于内部。与OE相比,IE中淀粉合成相关酶的表达模式发生了显着变化。双相淀粉颗粒内的颗粒结合淀粉合酶I活性略有下降。IE 比 OE 经历了更严重的缺氧应激,并且上调的无氧呼吸途径表明碳消耗增加。由于缺乏足够的碳流入,IE中的淀粉经历了由弱到强的SBEIIb缺陷效应,导致双相淀粉颗粒的形成及其在胚乳中的区域分布。
更新日期:2020-03-19
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