发掘玉米抗病种质资源,克隆抗病基因, 并解析玉米抗病机制,是玉米抗病性品种改良的基础。类病斑突变体 (Lesion mimic mutant,Lmm)是一类在没有病原菌侵染或其他外界刺激情况下,表现出类似病害所致自发性坏死斑的突变体,是研究植物抗病机制的重要材料。本研究对类病斑突变体Lmm18进行了表型鉴定和基因初定位。该突变体首先在叶尖部表现类病斑坏死表型,坏死斑随着生长沿叶脉逐渐扩展增多,最后遍及整个叶片。通过DAB(3,3’-diaminobenzidine)染色,我们发现Lmm18中过氧化氢含量相较于野生型明显增多。此外,抗病标志基因PATHOGENESIS-RELATED 1(PR1)和PR5在Lmm18中显著上调,表明该突变体启动了抗病防御反应。遗传分析表明,该性状由显性单基因控制。我们利用B73与Lmm18杂交构建的F2群体进行BSR-Seq(Bulked Segregant RNA-Sequencing)分析及连锁标记定位,将LMM18基因初步定位到2号染色体1.23 Mb的区间内,为后续克隆该基因并解析其介导的抗病防御调控机制奠定了基础。

Identifying the disease resistant maize germplasm, cloning of the casual genes as well as dissecting the associated mechanism constitute the basis for molecular improvement to obtain disease-resistant maize varieties. Lesion mimic mutants (Lmm/lmm) are a series of mutants that display disease-like spontaneous lesions in the absence of pathogen infection and other stimulus. In this study, we characterized the phenotype of Lmm18 mutant and performed initial mapping of the causal gene. Small necrotic lesions were initially visible on the tips of the leaves then expand along with veins to the whole leaves eventually. Hydrogen peroxide accumulation was found increased dramatically in Lmm18 compared to the wild type by DAB (3,3’-diaminobenzidine) staining. Besides, disease resistance marker genes PATHOGENESIS-RELATED 1 (PR1) and PR5 were also significantly up-regulated in Lmm18, indicating activated defense response. Further genetic analysis showed that Lmm18 was controlled by a single dominant gene. We performed BSR-Seq analysis using the F2 population generated by cross between B73 and Lmm18. The causal gene has been initially mapped to the region of 1.23 Mb on chromosome 2, which is the basis for subsequent gene cloning and dissection of LMM18-mediated defense regulation.

河南省杰出青年科学基金项目(212300410007)、NSFC-河南联合(U2004207)、河南省“中原千人 计划”中原青年拔尖人才项目(ZYQR201912168)、2022年度省级科技研发计划联合基金(应用攻关类)(222103810003)