山东省不同时期主推小麦品种的籽粒淀粉合成比较

Comparison in Grain Starch Biosynthesis of the Leading Wheat Cultivars of Different Eras Released in Shandong Province

籽粒淀粉含量对小麦产量和加工品质有重要影响,本实验对1949年以来山东省不同时期8个主要小麦推广品种籽粒灌浆过程中淀粉含量、淀粉合成关键酶活性和酶基因表达的动态变化进行了比较,以期为小麦遗传改良提供理论依据。结果表明,8个小麦品种籽粒总淀粉含量和直、支链淀粉含量随着育成时间的推移表现明显的上升趋势,与籽粒产量的变化一致。籽粒灌浆过程中,淀粉合成关键酶ADP-葡萄糖焦磷酸化酶(AGPase)、淀粉粒束缚淀粉合酶(GBSS)和淀粉分支酶(SBE)活性及其编码基因相对表达量呈单峰模式,在花后20 d达到顶峰;可溶性淀粉合酶(SSS)花后10 d以后呈缓慢下降的趋势。AGPase和SSS活性及其编码基因相对表达量随着品种育成年代的推移呈上升的趋势,近年选育的‘济南17’和‘济麦22’显著高于其他品种,而GBSS和SBE酶活性及其编码基因表达量变化趋势不明显。相关分析结果表明,AGPase和SSS酶活性及其编码基因表达水平与成熟期籽粒淀粉含量的相关性高于GBSS和SBE酶,说明胚乳淀粉合成在提高小麦籽粒产量方面具有重要作用,AGPase和SSS对淀粉含量的影响可能超过GBSS和SBE。

Grain starch plays a very important role in determining wheat yield and quality. Eight leading wheat cultivars widely planted in Shandong province during different decades since 1949 were investigated in this study. The dynamic change of starch content, starch biosynthesis of historical wheat cultivars during grain filling released in Shandong province were compared in order to extend the current view and provide the theoretical basis for wheat breeding. A comprehensive analysis of the starch biosynthesis in developing endosperm and the activities of starch biosynthetic enzymes and the transcript levels of the encoding genes were investigated. The results revealed that the content of amylose, amylopectin and total starch content in mature endosperm increased significantly with the released time of eight wheat cultivars, in accordance with changes in the grain yield. During the grain filling, the activities of starch biosynthetic enzymes and relative expressions of their encoding genes showed unimodal patterns peaking around 20 days after anthesis （DAA）, such as ADP-glucose pyrophosphorylase （AGPase）, granule-bound starch synthase （GBSS）, and starch branching enzyme （SBE）. Whereas, the activity of soluble starch synthase （SSS） and their transcript levels declined gradually after 10 DAA. The activities and relative expressions of AGPase and SSS genes increased pronounced with the cultivar evolution, especially for the newest cultivars such as ＇Jinan17＇ and ＇Jimai22＇ with the highest activities and expression levels. However, the expression levels of GBSS and SBE varied insignificantly with the released time. The activities and gene expression levels of AGPase and SSS were more related to the starch content in mature seeds compared to that of GBSS and SBE, suggesting their more important roles in starch biosynthesis. Therefore, grain yield could be improved in future breeding program by modification in starch physicochemical properties through screening of key enzyme activities and expressions involved in starch biosynthesis during developing endosperm.