Transcriptomic Analysis of Cold Stress-responsive Genes in Brassica oleracea

Low temperature is one of the most severe environmental factors that encumber cabbage (Brassica oleracea var. capitata) production, especially at the seedling stage in temperate countries and cold tolerant cultivars are imperative to address this issue. To get deeper insight into its cold tolerance mechanisms of cabbage, we have analyzed transcriptomics of a cold tolerant and a cold susceptible line of cabbage after applying cold stress by Illumina Hiseq 2000 short read (paired-end) sequencing technology. A total of 58,094 unigenes were obtained by de nova assembly and were assigned Nr annotations. Functional classification revealed the involvement of unigenes in various biological processes, highlyaccounted with cellular process and metabolic process. We identified 12,578 unique cold-responsive candidate genes with significantly differential expression between control and treated samples. Of which, 5,792 genes were up-regulated while 6,786 genes were down-regulated. Accordingly, 19 up and down-regulated unigenes were validated by real-time PCR expression analysis in the same lines of cabbage. Thus, the transcriptome dataset of B. oleracea will provide valuable gene resources for future application in crop improvement. In addition, this study sets a good example for large-scale identification of cold-responsive genes in non-model organisms using the sequencing-based approach.