John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK.
New Phytol. 2020 Dec;228(5):1490-1504. doi: 10.1111/nph.16858. Epub 2020 Sep 9.
Starch granules are composed of two distinct glucose polymers - amylose and amylopectin. Amylose constitutes 5-35% of most natural starches and has a major influence over starch properties in foods. Its synthesis and storage occurs within the semicrystalline amylopectin matrix of starch granules, this poses a great challenge for biochemical and structural analyses. However, the last two decades have seen vast progress in understanding amylose synthesis, including new insights into the action of GRANULE BOUND STARCH SYNTHASE (GBSS), the major glucosyltransferase that synthesises amylose, and the discovery of PROTEIN TARGETING TO STARCH1 (PTST1) that targets GBSS to starch granules. Advances in analytical techniques have resolved the fine structure of amylose, raising new questions on how structure is determined during biosynthesis. Furthermore, the discovery of wild plants that do not produce amylose revives a long-standing question of why starch granules contain amylose, rather than amylopectin alone. Overall, these findings contribute towards a full understanding of amylose biosynthesis, structure and function that will be essential for future approaches to improve starch quality in crops.
淀粉颗粒由两种不同的葡萄糖聚合物组成 - 直链淀粉和支链淀粉。直链淀粉构成了大多数天然淀粉的 5-35％，对食品中淀粉的性质有重大影响。它的合成和储存发生在淀粉颗粒的半结晶支链淀粉基质内，这对生化和结构分析构成了巨大挑战。然而，在过去的二十年中，人们对直链淀粉合成有了深入的了解，包括对合成直链淀粉的主要糖基转移酶 - 颗粒结合淀粉合成酶（GBSS）的作用的新见解，以及发现将 GBSS 靶向淀粉颗粒的蛋白靶向淀粉 1（PTST1）。分析技术的进步解决了直链淀粉的精细结构问题，提出了在生物合成过程中如何确定结构的新问题。此外，发现不产生直链淀粉的野生植物重新引发了一个长期存在的问题，即为什么淀粉颗粒含有直链淀粉，而不是仅含有支链淀粉。总的来说，这些发现有助于全面了解直链淀粉的生物合成、结构和功能，这对于未来改进作物淀粉质量的方法至关重要。
