He Shutao, Hao Xiaomeng, Wang Shanshan, Zhou Wenzhi, Ma Qiuxiang, Lu Xinlu, Chen Luonan, Zhang Peng
National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China.
Key Laboratory of Systems Biology, CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China.
J Exp Bot. 2022 Apr 18;73(8):2540-2557. doi: 10.1093/jxb/erac022.
Starch is a glucose polymer synthesized by green plants for energy storage and is crucial for plant growth and reproduction. The biosynthesis of starch polysaccharides is mediated by members of the large starch synthase (SS) protein superfamily. Here, we showed that in cassava storage roots, soluble starch synthase II (MeSSII) plays an important role in starch biosynthesis and the formation of protein complexes with other starch biosynthetic enzymes by directly interacting with MeSSI, MeSBEII, and MeISAII. MeSSII-RNAi cassava lines showed increased amylose content and reduced biosynthesis of the intermediate chain of amylopectin (B1 type) in their storage roots, leading to altered starch physicochemical properties. Furthermore, gel permeation chromatography analysis of starch biosynthetic enzymes between wild type and MeSSII-RNAi lines confirmed the key role of MeSSII in the organization of heteromeric starch synthetic protein complexes. The lack of MeSSII in cassava also reduced the capacity of MeSSI, MeSBEII, MeISAI, and MeISAII to bind to starch granules. These findings shed light on the key components of the starch biosynthesis machinery in root crops.
淀粉是绿色植物合成的一种葡萄糖聚合物，用于能量储存，对植物的生长和繁殖至关重要。淀粉多糖的生物合成由大型淀粉合酶（SS）蛋白超家族的成员介导。在此，我们表明，在木薯块根中，可溶性淀粉合酶II（MeSSII）通过与MeSSI、MeSBEII和MeISAII直接相互作用，在淀粉生物合成以及与其他淀粉生物合成酶形成蛋白质复合物中发挥重要作用。MeSSII-RNAi木薯品系的块根中直链淀粉含量增加，支链淀粉中间链（B1型）的生物合成减少，导致淀粉理化性质改变。此外，对野生型和MeSSII-RNAi品系之间的淀粉生物合成酶进行凝胶渗透色谱分析，证实了MeSSII在异源淀粉合成蛋白复合物组织中的关键作用。木薯中缺乏MeSSII也降低了MeSSI、MeSBEII、MeISAI和MeISAII与淀粉颗粒结合的能力。这些发现揭示了块根作物淀粉生物合成机制的关键组成部分。
