Transcriptomic insights into differential cold tolerance of two tobacco cultivars

Purpose: we conducted a six time-point transcriptomic analysis using two tobacco cultivars with contrasting cold responses, Taiyan8 tobacco (TT, cold susceptibility) and Yanyan97 tobacco (YT, cold resistance). Methods: mRNA profiles of Tobacco seedlings from CK and cold-treated plants were generated by deep sequencing, in triplicate, usingIllumina Hiseq4500. The sequence reads that passed quality filters were analyzed at the transcript isoform level with methods: hisat2 (v2.0.5), SAMtools (v1.9). StringTie (v1.3.4d) and FeatureCounts (v1.6.4) Results: We found that both cultivars had common mechanisms to cope with cold stress, including common differentially expressed genes (DEGs), similar time-point-related differential expression profile of genes, and similar NtCBF gene co-expression modules, suggesting conservation of adaptation strategies for cold responses. Importantly, we found that YT experienced DEGs even under normal growth condition and had less DEGs in early stage of cold stress (0.5-2 h) when compared to TT, reflecting occurrence of genotype-dependent gene transcription. Moreover, a gene co-expression module (brown) with stress-related genes up-regulated in YT instead of TT at late stage (4-8 h), which might contribute to contrasting phenotypic changes during cold stress between TT and YT. Conclusions: our study provides valuable resources for transcriptomic studies of cold responses in plants. It also helps to identify key cold responsive genes for genetic manipulation for breeding of tobacco cultivars in the future. Tobacco seedlings at the five-leaf stage were used for cold treatment at 4℃. Leaves from CK and cold-treated (0.5h,1h,2h,4h and 8h) plants were collected at different time points and immediately frozen in liquid nitrogen for RNA preparation. Each sample was biologically triplicated for transcriptomic analyses.