LbHSP17.9 Participated in the Regulation of Cold Stress in Cut Lily Flowers

Heat shock proteins (HSPs) play important roles in plant stress resistance, but it is not clear whether small molecular HSPs (sHSPs) are involved in the cold stress resistance of lily flowers. In this study, we cloned LbHSP17.9 and found that its expression was up-regulated under cold stress. When LbHSP17.9 was silenced (TRV2::LbHSP17.9) using virus-induced gene silencing in cut lily flowers, the content of malondialdehyde was increased under 4 degrees C stress treatment. The catalase (CAT) activity in TRV2::LbHSP17.9 was significantly lower than in TRV2 in the first 7 days, and the peroxidase (POD) activity in TRV2::LbHSP17.9 was significantly lower than in TRV2 after 4 days of 4 degrees C stress. Further analysis showed that the transcription levels of LbCu/ZnSOD, LbMnSOD and LbCAT in TRV2::LbHSP17.9 were lower than those of TRV2 under 4 degrees C stress. When LbHSP17.9 was overexpressed in lily petal disks, the OE-LbHSP17.9 disks faded later than the controls at 4 degrees C and the relative conductivity decreased significantly. Overexpression of LbHSP17.9 in Arabidopsis thaliana resulted in fewer injury symptoms and lower MDA content than wild type under 4 degrees C stress. Therefore, we speculate that LbHSP17.9 can improve the resistance of lily flowers to cold stress.