Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan 430030, China; The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agricultural and Food Innovation, Brisbane, QLD 4072, Australia.
The University of Queensland, School of Agriculture and Food Sciences, Brisbane, QLD 4072, Australia.
Carbohydr Polym. 2015;127:116-23. doi: 10.1016/j.carbpol.2015.03.046. Epub 2015 Apr 1.
Callus (formed when a plant tissue is wounded) is a promising system for studying starch biosynthesis and bioengineering; however the molecular structure of callus starch has been poorly characterized. Size-exclusion chromatography was used in this study to characterize the starch structure in rice calli from two cultivars and a mutant of one cultivar lacking starch branching enzyme IIb. There were major qualitative differences in the chain-length and whole-molecule size distributions between starch from grain and from callus. However callus starch was found to be able to simulate the starch metabolism from both leaves and endosperm and reveal the structural development of starch granules, and this was dependent on the culture system. During synthesis, trans-lamellar amylopectin chains in callus are synthesized earlier than single-lamella chains, while enzymatic degradation starts from outer to inner amylopectin chains. The outer layers of the callus-starch granules have larger molecules with lower amylose content and shorter amylopectin chains compared to further inside the callus-starch granules. Controlling starch granular number and size thus has potential for improving both the quantity and quality of plant starch.
愈伤组织（当植物组织受伤时形成）是研究淀粉生物合成和生物工程的有前途的系统；然而，愈伤组织淀粉的分子结构尚未得到很好的描述。本研究使用凝胶渗透色谱法对来自两个品种的水稻愈伤组织和一个缺乏淀粉分支酶 IIb 的品种的突变体的淀粉结构进行了表征。来自谷物和愈伤组织的淀粉在链长和整个分子大小分布方面存在主要的定性差异。然而，发现愈伤组织淀粉能够模拟来自叶片和胚乳的淀粉代谢，并揭示淀粉颗粒的结构发育，这取决于培养系统。在合成过程中，愈伤组织中的跨层支链淀粉链比单链淀粉链更早合成，而酶降解则从外到内的支链淀粉链开始。与愈伤组织淀粉颗粒内部相比，愈伤组织淀粉颗粒的外层具有更大的分子、更低的直链淀粉含量和更短的支链淀粉链。因此，控制淀粉颗粒数量和大小有可能提高植物淀粉的数量和质量。
