Identification of candidate genes for low temperature tolerance during germination of maize using a genome-wide association study and RNA-sequencing

Background: Maize ( Zea mays L.) is the largest agricultural crop in the world based on acreage and yield, however, it is inherently sensitive to low temperatures. The growth and yield of maize can be affected by low temperature during its whole growth period, particularly during germination. Therefore, it is urgent to identify the new gene(s) related to the low temperature tolerance during maize germination. Results: In this study, 14 phenotypic traits related to seed germination were used to explore the genetic architecture of maize through genome-wide association analysis (GWAS). A total of 30 single nucleotide polymorphisms (SNPs) associated with low temperature tolerance were detected (–log10( P ) > 4); 14 candidate genes were detected as being directly associated with these SNPs and 81 candidate genes were identified when the screen was extended to a distance of 30 kb from these SNPs. The candidate genes were predicted by conjoint analysis with RNA-sequencing (RNA-seq) to evaluate whole-genome gene expression levels. A total of nine differentially expressed genes (DEGs) (|log2foldchange|≥0.585， P <0.05) were found within distance of 30 kb, including two DEGs ( GRMZM2G101383 and GRMZM2G402584 ), which were associated with SNPs directly. The differential expression of these candidate genes was verified using qRT-PCR. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) terms of DEGs GRMZM2G052129 and GRMZM2G038964 were, ‘fatty acid metabolic process’, ‘Mitogen-activated protein kinase (MAPK) signal transduction’, and so on, which are related to the fluidity of the cell membrane and low temperature signal transduction. Conclusion: Therefore, further functional analysis of GRMZM2G052129 and GRMZM2G038964 will provide valuable information for understanding the genetic mechanism of low temperature tolerance during germination in maize.

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