水稻白叶枯病抗病机制与抗病育种展望

Mechanisms of disease resistance to bacterial blight and perspectives of molecular breeding in rice

水稻白叶枯病抗病基因的发掘与育种利用是目前针对白叶枯病害(Xoo)最环保和有效的手段。迄今,已报道至少45个抗白叶枯病抗性基因(Xa),本文对已报道基因的发掘和定位进行了总结,并根据蛋白结构与抗病机制对其中已克隆的15个Xa基因进行了分类,包括:(1)编码蛋白激酶受体的抗性基因,如RLK(receptor-like kinase);(2)编码NLR (nucleotide-binding leucine-rich repeat)免疫受体的抗性基因;(3)糖转运蛋白SWEET编码基因;(4)抗性执行基因(executor);(5)其他类型基因。Xa21作为第一个被克隆的白叶枯抗性基因,其编码蛋白RLK所介导的抗病机制已较为清晰。研究发现,除编码RLK的Xa基因外,大部分Xa发挥功能依赖于Xoo III型分泌系统分泌的类转录激活效应因子(transcriptionalactivator-likeeffectors,TALE)。很多受白叶枯菌分泌的TALE效应因子调控表达的水稻Xa基因实际为感病基因,其隐性突变产生抗病性。目前为止,白叶枯病non-TALE效应因子与抗病蛋白互作尚无报道,因此,突破口将是对编码NLR的Xa基因的抗病机制的研究。本文结合Xa的来源、抗谱、机制的研究及当前抗病育种存在的问题,针对白叶枯病广谱抗病分子育种提出了展望。

Discovery and utilization of resistance genes is the most environmentally-friendly and effective means to control bacterial blight disease caused by Xanthomonas oryzae pv. oryzae(Xoo). To date, at least 45 bacterial blight resistance genes(Xa) have been reported, with 15 genes functionally identified. In this review, we sum the discovery of these Xa genes, and focus on the 15 cloned Xa genes that are classified into five types according to protein structure and related mechanisms:(1) resistance genes encoding kinases, including RLK(receptor-like kinase);(2) resistance gene encoding NLR(nucleotide-bounding leucine-rich repeat proteins) receptor proteins;(3) sugar transporter SWEET encoding genes;(4) executor genes;(5) other type of resistance genes. As the first cloned Xa gene, Xa21 has been extensively studied. Interestingly, most of Xa genes are regulated by the Xoo-encoded transcriptional activator-like effectors(TALE) secreted through the type III secretory, which are mainly susceptibility(S) genes and their mutation alleles confer Xoo resistance. So far, no non-TALE effector-XA protein interaction has been reported. Further investigations may be focused on the NLR genes that recognize the cognate non-TALE effectors in the rice-Xoo pathosystem. Based on the study of the origin, resistance function and mechanisms of Xa genes, and considering needs in disease resistance breeding, we propose the perspective of molecular breeding for broad-spectrum bacterial blight resistance.