茶树耐铝特性与偏喜铵特性的关联机理研究

Tea plant (Camellia sinensis) is a kind of crop species that is both aluminium (Al) tolerance and ammonium preference. There are extensive reports on the response of plants to Al toxicity and nitrogen sources, but Al toxicity and nitrogen utilization are often studied separately. Little information was reported about mechanism that link Al stress and nitrogen nutrition. The characteristics of Al tolerance in tea plant may be related to nitrogen metabolism through the analysis of literature and we hypothesized that the mechanism of close relationship between Al tolerance and ammonium preference in tea plant has evolved the progress of nitrogen metabolism. Two varieties of typical clonal tea plants will be chosen for the present study. The effects and the molecular mechanism of Al and ammonium on the activities and its main metabolites of the three enzymes (glutamine synthetase, glutamate dehydrogenase and phenylalanine ammonialyase) will be studied based on the previous work in order to reveal the relationship between nitrogen metabolism progress and Al tolerance and ammonium preference. The results obtained will not only enrich the mechanism of Al tolerance and ammonium preference in plants but also provide the effective theory basis for improving the capacity of Al tolerance and the utilization of nitrogen in acid soil.

茶树是一种既耐铝又喜铵的作物，关于植物对铝毒和氮素响应的研究有很多，但对两者的研究都是独立进行的，而将植物耐铝毒和氮素吸收利用关联起来的机理研究则鲜少报道。通过分析资料推测茶树耐铝特性可能与氮素代谢有关，并假设氮素代谢的某些过程是茶树耐铝特性与喜铵特性关联的机理。据此，本项目在已有的研究基础上，采用两种典型的无性系茶树种植品种，以与铵态氮代谢相关的三种酶（谷氨酰胺合成酶、谷氨酸脱氢酶和苯丙氨酸解氨酶）为出发点，研究外源铝和铵态氮供应对这三种酶的活性及其代谢产物的影响，并从基因表达角度研究其分子机理，探讨氮代谢相关过程与茶树耐铝、喜铵的关系，以期从氮代谢角度解释茶树耐铝特性与偏性吸收铵态氮的关联机理。研究结果不仅能丰富植物耐铝和喜铵的相关机制，也可为提高酸性土壤植物的耐铝能力和氮素利用率提供理论依据。

茶树是我国主要的经济作物，对国内消费和出口创汇都具有重要意义。本项目利用已有研究基础，调查了典型茶园土壤与对应茶树体内养分元素的情况，结果显示江苏茶园土壤肥力总体状况良好，土壤中有机质、氮、磷、钾含量丰富，个别茶园磷、钾含量偏低，在施肥管理过程中要特别注意磷钾肥的施用；用无性系茶树种植品种，在铝铵处理下，研究茶树体内谷氨酰胺合成酶GS、谷氨酸脱氢酶GDH和苯丙氨酸解氨酶PAL的活性及其代谢组分的变化结果显示GS活性呈显著性差异，按活性大小顺序依次为纯NO3 >NH4+Al>纯NH4> NO3+Al；纯NH4处理的GDH活性最高，而纯NO3处理的GDH活性最低；纯NO3处理的PAL酶活性最高；并从转录组学水平上研究了茶树对不同氮源的响应，获得的差异表达基因（DEGs）表明，铵态氮处理的茶树次生代谢途径中的DEGs明显比硝态氮处理及铵硝配施处理的DEGs丰富，证明了茶树偏好铵态氮的特性。研究结果可为提高酸性土壤植物氮素利用效率以及茶园科学合理施肥提供理论依据。