荔枝受体激酶LcRLK1对霜疫霉侵染的响应及其抗性调控机制

Litchi is an important fruit in our country, but its production has been affected by downy blight disease. Thus, it is urgent to deepen the research of resistance molecular mechanism. Receptor-like kinases (RLKs) mainly distributed on the membrane of cell, which can recognition signals of pathogen infection and play an important role in the resistance response of host. In the model plant, the research has made great advance on the function and action mode of RLKs in the disease resistance, but the study in fruit trees is severely lagging behind. In the previous work, we have cloned a RLK, named as LcRLK1. The LcRLK1 is induced up to a higher level after infection of pathogen, and the expression of LcRLK1 in the resistant cultivar was significantly higher than that of the susceptible cultivar. LcRLK1 is at the central position in the early genes response to the pathogen, suggesting that LcRLK1 played an important role in the signal recognition and transduction after pathogen infection. In the following research, the early responses of LcRLK1 to different pathogen-related molecular models will be investigated, providing theoretical support for inducing resistance in litchi. The interacting protein of LcRLK1 will be screened by yeast two-hybrid technique. A regulatory network will be constructed about the downstream genes induced by LcRLK1. Through these study, the response of LcRLK1 to the pathogen infection will be elucidate, and the molecular basis of LcRLK1 on resistance will be revealed in litchi.

荔枝是我国重要特色水果，但生产上霜疫霉病危害严重，因而亟待加深其对抗性分子机制的研究。受体激酶（RLKs）主要分布在质膜上，能识别病原菌侵染信号，在寄主的抗性反应中发挥重要作用。模式植物上，RLKs在抗病性中的功能和作用方式已较为明确，但木本果树中的研究还鲜见报道。前期的工作中，荔枝LcRLK1在抗性品种中受霜疫霉菌诱导表达，且表达量显著高于感病品种；共表达分析显示其在病原早期应答基因中居于核心调控位置，暗示LcRLK1在病原菌的识别和信号传导中发挥重要作用。在此基础上，通过调查LcRLK1对不同病原相关分子模式的早期响应方式，为诱导抗性提供理论支撑；通过酵母双杂交技术筛选LcRLK1互作蛋白，并对受LcRLK1诱导的下游基因进行调控网络分析。从而阐明LcRLK1对霜疫霉菌侵染的响应及其对抗性的调控机制，揭示LcRLK1在荔枝抗性应答中的分子基础。

荔枝是我国重要特色水果，但生产上霜疫霉病危害严重，因而亟待加深对抗性分子机制的研究。荔枝LcRLK1是1个受体类激酶蛋白，受霜疫霉菌侵染被诱导表达，其在对病原的早期应答反应中居于核心调控位置。LcRLK1-eGFP融合蛋白的亚细胞定位结果表明其蛋白分布在细胞质膜外侧。与对照相比，本氏烟叶片中瞬时超表达LcRLK1能显著抑制辣椒疫霉菌的定殖。转基因叶片显著提高了对辣椒疫霉菌的抗病性，证实LcRLK1在霜疫霉病抗性中发挥重要作用。构建了荔枝果皮酵母单杂和双杂文库，筛选到3个与LcRLK1基因核心启动结合的转录因子，但未能筛选到与LcRLK1作用的互作蛋白，可能与其主要分布在细胞质膜外侧有关。对果实的采前诱抗剂处理实验证实超敏蛋白等不仅能提高荔枝对霜疫霉病的抗性，而且还在早期诱导抗性基因LcRLK1的上升表达。LcRLK1上升表达后，下游的差异表达基因主要参与苯丙烷生物合成和植物激素信号转导等抗病相关途径。这些发现不仅丰富了荔枝对霜疫霉病抗性机制的认识，而且为开展荔枝诱抗防治提供了分子依据和理论基础。