水稻钾离子转运蛋白OsHAK在拟禾本科根结线虫侵染中的功能研究

Meloidogyne graminicola is one of the most dangerous plant parasitic nematodes in rice. Infection by M. graminicola in rice induces the formation of malformed root, suppresses the up taking inorganic salt from soil. The up taking and accumulation of potassium are significantly reduced in rice infected with M. graminicola. Potassium is an essential and abundant nutrient in plant cells, plays many important regulatory roles in plant disease resistance. However, it is little known about the role of potassium metabolism in rice resistance to M. graminicola. We found that OsHAKs, the K+ transporter family genes were significantly induced by M. graminicola inoculation. In this study, we will focus on the functional characterization of OsHAK, through analysis of the subcellular localization, expression pattern and the and phenotype of overexpression and CRISPR/Cas9 plants upon stresses of K+ deficiency and M. graminicola. The aim of this study was to analyze the change of potassium accumulation in the host induced by M. graminicola, and the function of OsHAK against M. graminicola. This project will be beneficial to understand the molecular mechanism of potassium metabolism in the intercaction between rice and M. graminicola and provides important basis for controlling M. graminicola with applying potassium fertilizer.

拟禾本科根结线虫是危害水稻的重要植物寄生线虫，可导致水稻根系发育畸形，影响对无机盐的吸收。拟禾本科根结线虫的侵染降低水稻对钾离子吸收和积累，钾元素是植物生长的必须大量元素之一，而且可以提高植物的抗病性。然而，钾离子代谢对水稻抗拟禾本科根结线虫的作用机制并不清楚。本项目在前期研究发现拟禾本科根结线虫的侵染诱导水稻钾离子转运蛋白家族基因OsHAKs上调表达的基础上，进一步通过发育表达模式分析、亚细胞定位、超表达和CRISPR/Cas9等分子生物学手段，研究鉴定OsHAK在水稻抗拟禾本科根结线虫中的作用，旨在解析拟禾本科根结线虫诱导的寄主内钾元素积累的变化，及钾离子转运蛋白OsHAK的抗病功能，研究结果有助于了解拟禾本科根结线虫与水稻互作过程中的钾代谢途径机制，为利用合理施加钾肥提高水稻对拟禾本科根结线虫的抗性提供理论依据。

拟禾本科根结线虫在我国南方水稻种植区发生面积逐年扩大，严重威胁水稻生产安全。施用钾肥能有效减少植物病害的发生，提高作物产量。我们研究了钾离子诱导水稻对根结线虫的抗性，进一步探讨了诱导抗性机制，并对钾离子通道和转运系统在水稻抗根结线虫过程中的作用和功能进行了初步地研究。K2SO4 处理水稻降低了根结线虫的侵染和发育水平，有效提高了水稻对根结线虫的抗性。K2SO4 诱导的抗性不是通过影响水稻根对根结线虫的吸引力和根结线虫取食位点巨细胞的发育来实现的。K2SO4 处理增强了水稻根中胼胝质沉积，并快速激发过氧化氢（H2O2）的 积累，从而启动水稻对根结线虫的基础防御。K2SO4 处理上调了水稻中抗病相关基因的表达。在根结线虫侵染初期，水稻中 JA / ET / BR 信号通路相关基因和病程相关蛋白基因 OsPR1a 和 OsPR1b 的 表达水平在 K2SO4 处理组中显著地高于未处理组。 钾离子通道蛋白 OsAKT1 和转运蛋白 OsHAK5 在水稻抗根结线虫中既有 其独立的作用，又参与了K2SO4诱导的抗性机制。不论是加K2SO4还是不加K2SO4 处理，这两种基因缺陷型植株中的根结数目和线虫数量均高于野生型植株，而在这两种基因缺陷型植株中 K2SO4 诱导的抗性都弱于在野生型植株中。钾离子转运蛋白OsHAKP 极可能定位在细胞膜上，并在细胞膜上与根结线虫 MgHIP 互作。OsHAKP 缺失会导致水稻对根结线虫的易感性提高，而超表达该基因则会提高水稻对根结线虫的抗性。