Comparative analysis of drought responsive transcriptome in Brassica napus genotypes with contrasting drought tolerance under different potassium levels

Abstract

Drought is a major limiting factor of Brassica napus (rapeseed) and potassium (K) plays important roles in rapeseed drought tolerance. Previous studies have reported that rapeseed cultivars characterized by different K status showed contrasting drought tolerance. However, the molecular mechanism underlying drought tolerance remains unclear. In this study, comparative transcriptome analysis was conducted between drought-tolerant cultivar Youyan57 and drought-sensitive cultivar Chuanyou36 exposed to PEG6000 simulated drought stress with two K levels (1.0 and 0.01 mM K2SO4, referred to NK and LK, respectively). A total of 1689 differentially expressed genes (DEGs) were identified at NK. DEGs involved in photosynthesis, glutathione biosynthesis, IAA signal transduction were up-regulated in Youyan57 at NK. By contrast, the down-regulated DEGs were significantly enriched in biosynthesis of amino acids, cysteine and methionine metabolism and glucosinolate biosynthesis. Transcription profile was affected seriously at LK treatment since only 1050 DEGs were identified. DEGs involved in biosynthesis of amino acids reduced largely. Furthermore, the conspicuous up-regulation of protein phosphatase 2 C in Chuanyou36 could lead to more severe drought stress at LK, which negatively participated in abscisic acid (ABA) signal transduction. Taken together, the comparative transcriptome analysis identified a set of drought-regulated genes involved in several pathways, and provided important information about molecular mechanisms underlying rapeseed drought tolerance.