不同氮源调控水稻根系细胞壁结合态磷再利用的生理和分子机制

The reutilization of cell wall-bound P in rice roots can fully mobilize the P sink capacity in rice roots, improve the P use efficiency in rice plants, and alleviate the P deficiency stress in environment. The regulatory effects of different N forms on uptake, transport, and distribution of P in rice plants are significantly different. However, the key processes for reutilization of cell wall-bound P in rice roots regulated by N are still unclear. The physiological and molecular mechanisms of reutilization of cell wall-bound P in rice roots in response to the intervening of different N resources are still unknown. In this project, Nipponbare will be used as rice variety, ammonium and nitrate will be used as the regulating ways, and hydroponic experiment and field experiment will be combined together as the research method. The key genes and proteins involved in the process of two N forms regulating cell wall-bound P reutilization will be clarified, members of the pectin methyl esterase genes which showed significant differences in expression levels under two N forms condition and its function will be illuminated, the network pathways for signal chemicals (putrescine and ethylene) in the process of two N forms regulating reutilization of cell wall-bound P will be revealed, and the cultivation technology system for “N regulating P” to improve the P use efficiency in rice plants will be built. This study can provide theoretical basis and technical support for accelerating reutilization of P in rice plants, decreasing P application rate in paddy soil, and reducing the P eutrophication pollution in the environment.

水稻根系细胞壁结合态磷再利用可充分调动根系磷库容，提高植株磷利用效率，缓解缺磷胁迫。不同形态氮源对水稻磷吸收、转运、分配存在不同的调控作用。目前氮素介入水稻根系调控细胞壁结合态磷再利用的关键过程尚不清楚，水稻根系细胞壁结合态磷响应不同氮源介入的生理和分子机制尚不明确。本项目以水稻品种日本晴为供试材料，以铵态氮、硝态氮为外源氮素调控手段，通过水培试验和田间试验相结合的方法，阐明参与两种氮源调节水稻根系细胞壁结合态磷再利用的基因和蛋白，明确在两种氮源条件下表达量存在显著差异的果胶甲酯酶基因家族成员及功能，解析两种氮源调控细胞壁结合态磷再利用过程中信号物质腐胺和乙烯的网络途径，构建“以氮调磷”提高水稻磷利用效率的栽培技术体系，以期为促进水稻植株磷素再利用，降低土壤磷肥施用量，减少磷素富营养化污染提供理论基础和技术支持。

铵态氮和硝态氮对水稻磷吸收、转运和分配存在不同的调控作用，然而，两种氮源对水稻根系细胞壁结合态磷再利用的调控机制还不清楚。本项目以水稻品种日本晴为供试材料，以铵态氮、硝态氮为外源氮素调控手段，通过水培试验和田间试验相结合的方法，阐明参与两种氮源调节水稻根系细胞壁结合态磷再利用的基因和蛋白，明确在两种氮源条件下表达量存在显著差异的果胶甲酯酶基因家族成员及功能，解析两种氮源调控细胞壁结合态磷再利用过程中信号物质腐胺和乙烯的网络途径。本项目结果显示，缺磷条件下，铵态氮通过调控水稻根系腐胺和乙烯的合成，提高根系细胞壁果胶的合成和果胶甲酯酶的活性，从而提高根系细胞壁磷的再利用。果胶甲酯酶35个基因家族中，两种氮源对果胶甲酯酶活性的不同调节作用主要受OsPME9和OsPME29两个基因控制。转录组学结果显示，铵态氮还通过调控水稻根系水稻碳氮代谢系统、信号系统、抗氧化系统、转录因子系统等提高水稻在缺磷条件下对磷的吸收和再利用。该项目为构建“以氮调磷”提高水稻磷利用效率的栽培技术体系，降低土壤磷肥施用量，减少磷素富营养化污染提供理论基础和技术支持。

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