Phenotypic Analysis and Initial Gene Mapping of the Maize Lesion Mimic Mutant Lmm18
Identifying the disease resistant maize germplasm,cloning of the casual genes as well as dissecting the associated mechanism are the basis for molecular improvement to obtain disease-resistant maize varieties.Le-sion 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,phenotypic identification and initial gene mapping of the Lmm18 mutant were conducted.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.Additionally,disease resistance marker genes PATHOGENESIS-RELATED 1(PR1)and PR5 were also significantly up-regulated in Lmm18,indicat-ing activated defense response.Further genetic analysis showed that Lmm18 was controlled by a single dominant gene.BSR-Seq analysis was performed 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.
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