Expression Analysis of Flowering Regulatory Genes in Tobacco under Low Temperature Stress

To investigate the molecular regulatory mechanism of low temperature induced early flowering, a cold-sensitive tobacco cultivar Yunyan 87 was treated with cold stress of 12 ℃ for 14 days. The shoot apical tissues of plants were collected for flowering-regulatory gene expression analysis. The time of central flower opening and the total number of leaves were investigated. The results showed that central flower opening date of the cold-treated tobacco plants was 7 days earlier than that of the control, and total leaf number of the treated plants was 5 leaves less than that of the control. Besides, the expression levels of 10 flowering-regulatory genes were increased by cold stress when compared to the control, including NtMADS4, NtMADS11, NtAP1, NtSOC1, NtFUL, NtNFL1, NtFT1, NtFT3, NtFT4 and NtFT5; and then decreased to similar levels of the control after recovery under normal conditions for 7-14 days. These results suggested that cold-induced tobacco early flowering may be related to the up-regulation of these flowering regulatory genes.