低磷胁迫下油菜素内酯调控马铃薯淀粉合成机制的研究

Potato (Solanumtuberosum L.) has been grown as one of the four major food crops in China. However, the low soil phosphorus efficiency in potato growth area has severely restricted its yield and quality. Previous works have shown that BR can increase the biosynthesis of carbohydrate and the resistance to adverse conditions of plants. Our preliminary studies also denmonstrated that BR can significantly promote starch content in potato under low phosphorus condition. Therefore, BR could play a regulatory role in potato starch biosynthesis, especially under low phosphorus stress condition. To discover the mechanism, the effects of StCYP85A1, a key enzyme encoding gene in BR biosynthesis pathway, on starch biosynthesis will be investigated at gene, protein, cell and tissue levels. Transgenic potato with up- or down-regulated expression of StCYP85A1 will been generated, and the effects of endogenous and exogenous BR alterations on starch biosynthesis under low phosphorus condition will be examined. The expression level and enzyme activity of starch biosynthetic genes and proteins will also be compared. The completion of this project will not only clarify the biological function of StCYP85A1 and the molecular mechanism of BR in starch biosynthesis, but also provide research bases for the genetic breeding of potato with improved agronomic traits.

马铃薯为我国四大主粮作物之一，但其种植区土壤中磷的有效性极低, 严重制约了土豆的产量和品质。已有研究表明，BR可以显著增加植物碳水化合物的合成及抗逆性，我们近期的研究也发现低磷条件下外施BR后马铃薯苗中淀粉的含量显著增加。因此，推测低磷胁迫BR可能影响和调控马铃薯的淀粉合成。为阐明其相关机理，我们拟从基因、蛋白、细胞、组织等不同层面分析BR合成途径中的关键酶编码基因StCYP85A1在低磷胁迫下对土豆中淀粉合成的影响，并通过转基因技术改变马铃薯植株内源BR的含量，结合BR处理，从外源和内源两个角度分析BR是否能够缓解马铃薯的缺磷症状、增加块茎淀粉含量。再通过qRT-PCR、酶活测定等实验手段来研究BR是否可以调控淀粉合成相关基因的表达和酶活性。本项目的实施不仅可以阐明StCYP85A1的生物学功能，同时可以揭示BR调控低磷胁迫下马铃薯淀粉合成的分子机理，并为马铃薯的遗传改良奠定基础。

马铃薯是我国重要的经济作物，但其主栽区土壤磷的有效性很低，严重制约了马铃薯的产量和品质，提高马铃薯对低磷环境的应对能力十分必要。而已有研究表明BR可以显著增加植物碳水化合物的合成及抗逆性，为研究BR是否能够提高马铃薯对低磷环境的应对能力，本项目克隆了BR合成途径中的关键酶编码基因StCYP85A1，并通过转基因技术改变马铃薯植株内源BR的含量，结合外源BR处理，从内、外两个角度分析BR是否能够缓解马铃薯的缺磷症状、增加块茎淀粉含量。结果表明BR能够促进马铃薯淀粉合成，影响了马铃薯淀粉组成，改变其淀粉品质；提高马铃薯体内磷利用效率，但是对马铃薯磷吸收没有显著影响；增加马铃薯植株抗氧化性，并且能够调控植株元素间的相互作用，进而达到提升马铃薯对低磷环境的应对能力。本项目基本阐明了StCYP85A1的生物学功能，并且为揭示BR调控低磷胁迫下马铃薯淀粉合成的分子机理奠定基础，为在农业生产中BR应对植物营养缺乏逆境提供了理论依据。