Transcriptomic Analysis Reveals Candidate Genes Responding Maize Gray Leaf Spot Caused by Cercospora zeina.

Wenzhu He,Moju Cao,Yonghui Zhu,Lin Yang,Jie Chen,Yuanyuan He,Shibin Gao,Jun Tan,Junpin Yang,Haitao Tang,Xiao Zhang,Yifeng Leng,Hai Lan,Biao Zhang,Yan Li,Luchang Deng,Jiwei Kang,Tingzhao Rong

doi:10.3390/plants10112257

Abstract

Gray leaf spot (GLS), caused by the fungal pathogen Cercospora zeina (C. zeina), is one of the most destructive soil-borne diseases in maize (Zea mays L.), and severely reduces maize production in Southwest China. However, the mechanism of resistance to GLS is not clear and few resistant alleles have been identified. Two maize inbred lines, which were shown to be resistant (R6) and susceptible (S8) to GLS, were injected by C. zeina spore suspensions. Transcriptome analysis was carried out with leaf tissue at 0, 6, 24, 144, and 240 h after inoculation. Compared with 0 h of inoculation, a total of 667 and 419 stable common differentially expressed genes (DEGs) were found in the resistant and susceptible lines across the four timepoints, respectively. The DEGs were usually enriched in ‘response to stimulus’ and ‘response to stress’ in GO term analysis, and ‘plant–pathogen interaction’, ‘MAPK signaling pathways’, and ‘plant hormone signal transduction’ pathways, which were related to maize’s response to GLS, were enriched in KEGG analysis. Weighted-Genes Co-expression Network Analysis (WGCNA) identified two modules, while twenty hub genes identified from these indicated that plant hormone signaling, calcium signaling pathways, and transcription factors played a central role in GLS sensing and response. Combing DEGs and QTL mapping, five genes were identified as the consensus genes for the resistance of GLS. Two genes, were both putative Leucine-rich repeat protein kinase family proteins, specifically expressed in R6. In summary, our results can provide resources for gene mining and exploring the mechanism of resistance to GLS in maize.

Highlights

Cercospora spores predominantly overwinter in diseased plant debris that remains on the soil surface [2], and conidia produced by the fungus are disseminated onto corn plants by wind and rain splash [3]
-susceptible genotypes, between we investigated the Differentially expressed genes (DEGs) of two(>0.86)
The specific DEGs of R6 and S8 at these timepoints were enriched in ‘metabolic pathways’, and ‘biosynthesis of secondary metabolites’ (Figure S9b,c). These results suggested that the biosynthesis of secondary metabolic pathways was important in the gray leaf spot response, while the DEGs of R6 enriched more pathways than those of S8, including amino acid, starch and sucrose, and hormone biosynthesis

Summary

Introduction

Gray leaf spot (GLS) in maize, Cercospora zeina (C. zeina), is one of the most destructive foliar diseases. High humidity and mild temperature are favorable conditions for GLS infection [1]. The mature GLS lesions run parallel to leaf veins with rectangular spots ranging in color from gray to tan. They first appear as small tan spots at the bottom leaf, and as the disease develops, the entire leaves and stem become withered. The disease causes substantial losses in yield (from 20% to 60%, and even as high as 100%) in severe cases [4,5,6]

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Discussion

Conclusion