Key Laboratory of Crop Genetics and Physiology of Jiangsu Province/Key Laboratory of Plant Functional Genomics of the Ministry of Education, Yangzhou University, Yangzhou, 225009, China.
Co-Innovation Center for Modern Production Technology of Grain Crops of Jiangsu Province/Joint International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education, Yangzhou University, Yangzhou, 225009, China.
Plant Mol Biol. 2020 Jun;103(3):355-371. doi: 10.1007/s11103-020-00998-w. Epub 2020 Mar 19.
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.
在玉米 ae 突变体中，双相淀粉颗粒在胚乳发育过程中经历了较弱到较强的 SBEIIb 缺陷效应，导致由于支链淀粉的长侧链延伸，其外部没有双折射。在缺乏淀粉分支酶 (SBE) 的谷物胚乳中，通常会检测到双相淀粉颗粒的区域性分布。然而，它们的分子结构、形成机制和区域分布尚不清楚。在这项研究中，在玉米 ae 突变体的冠胚乳内部区域观察到双相淀粉颗粒，并且其外部具有梳状轮廓的取向结构较差。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) 进行了研究。IE 中的淀粉具有较低的直链淀粉含量和较高的支链淀粉长侧链比例，而双相淀粉颗粒的外部具有较少的直链淀粉和较多的支链淀粉长侧链。与 OE 相比，IE 中淀粉合成相关酶的表达模式发生了显著变化。双相淀粉颗粒内的颗粒结合淀粉合成酶 I 活性略有下降。IE 经历的缺氧应激比 OE 更严重，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 中的淀粉经历了从弱到强的 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。研究结果为理解双相淀粉颗粒提供了信息。
