Comparison of transcriptomes and gene expression profiles of two chilling- and drought-tolerant and intolerant Nicotiana tabacum varieties under low temperature and drought stress
Tobacco plants often encounter chilling and water scarcity conditions when grown in spring and early summer, leading to retarded growth and developmental abnormalities. The purpose of this study was to investigate comprehensive molecular mechanisms of response and adaptation of tobacco seedlings to chilling and drought stress. By newly developed and high-throughput Illumina Hiseq™ 2000 RNA-seq and Digital Gene Expression (DGE) analysis, we constructed two transcriptomes and 14 DGE libraries using the chilling- and drought-tolerant tobacco variety MS-K326 and relatively intolerant variety Yunyan203 during chilling stress at 2 °C for 48 h and air-drought stress for 48 h. From the sequencing results, 106 million 90-bp quality-reads were obtained from two transcriptomes, then assembled into 97,921 non-redundant unigenes with mean length of 653 nt. After annotation to noted databases, all unigenes were used as references to annotate DGE sequences. All DGE libraries were compared to investigate differential expression patterns between the two varieties MS-K326 and Yunyan203 under chilling and drought stress, and 63 genes were found to be differentially expressed in the chilling- and drought-treated tobacco seedlings. By investigating these commonly expressed genes and some other known stress tolerance increasing genes, we found that the stress-tolerant tobacco variety might increase its chilling and drought tolerance by (1) rationally regulating membrane fluidity via changing saturation of lipids and membrane components; (2) synthesising more macro-molecules stabilisers, and osmotic adjustment solutes, that is, osmolytes; (3) reducing reactive oxygen species production by adjusting photosynthesis components as well as eliminating reactive oxygen species by rapidly activating anti-oxidant enzymes. This study provides a global view of transcriptome response and gene expression profile differences between two tobacco varieties with different chilling and drought tolerance in response to low temperatures and drought stresses.