Pan Zhifen, Deng Xiaoqing, Li Qiao, Xie Rong, Zhai Huisheng, Zeng Xingquan, Luobu Zhaxi, Tashi Nyima, Li Zhongyi
Chengdu Institute of Biology, Chinese Academy of Sciences, No. 9 Section 4, Renmin South Road, Chengdu 610041, People's Republic of China.
University of the Chinese Academy of Sciences, No. 19 Yuquan Road, Beijing 100039, People's Republic of China.
J Agric Food Chem. 2021 Feb 3;69(4):1206-1213. doi: 10.1021/acs.jafc.0c05445. Epub 2021 Jan 22.
Starch biosynthesis in cereal crops is a complex pathway regulated by multiple starch synthetic enzymes. Starch synthase IIa (SSIIa) is well-known to be one of the major starch synthases and is very important in amylopectin biosynthesis. It has significant effects on grain composition and kernel traits. However, there are few reports on the association of natural variation of in barley and grain composition and characteristics. In this work, two SSIIa isoforms were first identified as SSIIa and SSIIa by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis, mass spectrometry, and Western blotting. Sequence analysis of the gene demonstrated that a 33 bp insertion coding a peptide of APPSSVVPAKK caused different SSIIa, e.g., SSIIa and SSIIa. Based on this molecular difference, a polymerase chain reaction marker was developed, which could be used to screen different genotypes easily. Kernel hardness of genotypes was significantly higher than that of Chinese barley cultivars. The proportion of genotypes was extremely low in Australian barley cultivars (5/24) and much higher in Tibetan hull-less barley cultivars (46/74), consistent with the end-use requirements of barley grain. This study provided new information in barley endosperm starch synthesis and indicated that it is valuable for choosing the preferred genotype according to the end-use requirements.
谷类作物中的淀粉生物合成是一个由多种淀粉合成酶调控的复杂途径。淀粉合酶IIa（SSIIa）是主要的淀粉合酶之一，在支链淀粉生物合成中非常重要。它对籽粒组成和谷粒性状有显著影响。然而，关于大麦中SSIIa自然变异与籽粒组成和特性之间关联的报道很少。在这项研究中，首先通过一维十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、质谱分析和蛋白质免疫印迹法鉴定出两种SSIIa同工型，分别为SSIIa和SSIIa。对该基因的序列分析表明，一个编码APPSSVVPAKK肽段的33 bp插入导致了不同的SSIIa，如SSIIa和SSIIa。基于这种分子差异，开发了一种聚合酶链反应标记，可用于轻松筛选不同的基因型。基因型的籽粒硬度显著高于中国大麦品种。在澳大利亚大麦品种中，基因型的比例极低（5/24），而在西藏裸大麦品种中则高得多（46/74），这与大麦籽粒的最终用途要求一致。本研究为大麦胚乳淀粉合成提供了新信息，并表明根据最终用途要求选择优选的基因型具有重要价值。
