John Innes Centre, Norwich Research Park, Norwich, UK.
J Exp Bot. 2019 Feb 5;70(3):771-784. doi: 10.1093/jxb/ery412.
Starch, the major storage carbohydrate in plants, is synthesized in plastids as semi-crystalline, insoluble granules. Many organs and cell types accumulate starch at some point during their development and maturation. The biosynthesis of the starch polymers, amylopectin and amylose, is relatively well understood and mostly conserved between organs and species. However, we are only beginning to understand the mechanism by which starch granules are initiated, and the factors that control the number of granules per plastid and the size/shape of granules. Here, we review recent progress in understanding starch granule initiation and morphogenesis. In Arabidopsis, granule initiation requires several newly discovered proteins with specific locations within the chloroplast, and also on the availability of maltooligosaccharides which act as primers for initiation. We also describe progress in understanding granule biogenesis in the endosperm of cereal grains-within which there is large interspecies variation in granule initiation patterns and morphology. Investigating whether this diversity results from differences between species in the functions of known proteins, and/or from the presence of novel, unidentified proteins, is a promising area of future research. Expanding our knowledge in these areas will lead to new strategies for improving the quality of cereal crops by modifying starch granule size and shape in vivo.
淀粉是植物中主要的储存碳水化合物，它在质体中合成半结晶、不溶性颗粒。许多器官和细胞类型在其发育和成熟过程中的某个阶段都会积累淀粉。淀粉聚合物支链淀粉和直链淀粉的生物合成相对较为清楚，并且在器官和物种之间大多是保守的。然而，我们才刚刚开始了解淀粉颗粒起始的机制，以及控制每个质体中的颗粒数量和颗粒大小/形状的因素。在这里，我们综述了理解淀粉颗粒起始和形态发生的最新进展。在拟南芥中，颗粒起始需要几种新发现的蛋白质，这些蛋白质在叶绿体中有特定的位置，并且也依赖于作为起始引物的麦芽寡糖的可用性。我们还描述了在谷类作物胚乳中颗粒生物发生的研究进展——在这些作物中，颗粒起始模式和形态存在很大的种间变异性。研究这种多样性是否是由于物种间已知蛋白质功能的差异，以及/或者是否存在新的、未被识别的蛋白质，是未来研究的一个有前途的领域。扩大我们在这些领域的知识将为通过在体内改变淀粉颗粒的大小和形状来提高谷类作物的质量提供新的策略。
