Auxin-related genes associated with leaf petiole angle at the seedling stage are involved in adaptation to low temperature in Brassica napus

Abstract

Rapeseed (Brassica napus L.) has winter and semi-winter ecotypes which need vernalization in the development process. Leaf development coincides with vernalization, and the leaf petiole angle (LPA) is associated with cold environmental adaptation during the overwintering period in rapeseed. In the present study, a genome-wide association study (GWAS) using a Brassica 60 K SNP array for LPA identified 45 significantly associated quantitative trait loci (QTLs) and 3525 candidate genes. Moreover, two rapeseed accessions (T193, winter type and T268, semi-winter type) with significantly different LPA degrees were used for RNA sequencing (RNA-seq). And transcriptome analysis revealed that most of the differentially expressed genes (DEGs) were involved in auxin, brassinosteroid (BR) and ethylene signaling pathways as well as the cell division pathway. Using integration of GWAS and RNA-seq analysis, several promising candidate genes, including BZR1, IAA7, IAA15, PIN3 and SPL orthologs were prioritized for further research. Quantitative real time PCR (qRT-PCR) also validated the differential expression patterns of nine candidate genes between T193 and T268. Through regulating differential cell division of the abaxial and adaxial petiole for small LPA, auxin signaling genes could be involved in the adaptation of rapeseed seedlings to low temperature conditions. These findings provide insights into the molecular mechanism of environmental adaptation at the seedling stage and provide valuable information for facilitating marker-based breeding in B. napus.