Expression Profiling of Genes Related to Antioxidant and Photosynthesis Capacity in Flue-Cured Tobacco Seedlings Subjected to Chilling Stress.

Tobacco is cultivated worldwide as an important economical leaf crop. However, frequent low temperature during the early spring season affects the growth and development of flue-cured tobacco seedlings, and decrease the yield and quality of flue-cured tobacco leaves in southern China. Seedlings of flue-cured tobacco strain K326 with 5–6 true leaves was placed for 3 days in a light incubator with 5-7 °C while the control group grew at normal temperature range of 23-25°C. The objective was to analyze physiological and ecological adaptations by measuring parameters related to levels of photosynthetic, oxidant, and antioxidant factors in the cell membranes of leaves; and differential expression of genes in flue-cured tobacco seedlings after chilling stress was analyzed by digital gene expression profiling technology. The results showed that malondialdehyde (MDA) contents and electrolyte permeability, the vitamin C (Vc) and glutathione (GSH) contents, activities of superoxide dismutase (SOD) and catalase (CAT) increased significantly after chilling stress while chlorophyll contents, the net photosynthetic rate, stomatal conductance and transpiration decreased significantly. Meanwhile, 1673 genes among 2357 genes differentially expressed significantly were upregulated, and 684 downregulated. The molecular functions of these differentially expressed genes were mainly associated with oxidoreductase activities and the antioxidant system of the cell membrane of flue-cured seedlings. As for metabolism pathways, genes related to photosynthesis-antenna proteins and photosynthesis were down regulated, while genes involved in oxidant capacity, such as Vc, GSH, and proline metabolism, were upregulated. Importantly, the results of gene expression analysis and physio-ecological adaptation were consistent to elaborate flue-cured seedlings altered photosynthetic, oxidant and antioxidant metabolism pathways by adjustment of gene expression to reduce the damage from chilling stress. Hence, it is feasible to analyze physio-ecological adaptation and differential gene expression of crops under stress, and this will facilitate further analysis gene ontology functions and gene expression relationships.