Silencing of SlHB2 Improves Drought, Salt Stress Tolerance, and Induces Stress-Related Gene Expression in Tomato

Adverse environmental conditions, such as drought, high salinity, and extreme temperature, severely affect the growth and productivity of crop plants. HD-Zip I transcription factors have been described to be involved in stress responses. In the present study, a novel transcription factor gene, SlHB2, from the HD-Zip I subfamily has been cloned from tomato. The expression of SlHB2 was induced by ABA, ACC, MeJA, dehydration, high-salinity, low-temperature, and wounding. To investigate the function of SlHB2 in response to abiotic stress, tomato seedlings of SlHB2-RNAi lines were exposed to drought and salt stresses. Higher levels of chlorophyll and water contents, lower water loss rate and MDA contents were detected in the leaves of transgenic plants compared to those in wild type under stress conditions, which was consistent with the enhanced tolerance of SlHB2-RNAi lines to drought and salt stresses. Significant up-regulation of multiple stress-related genes was also observed in the RNAi lines under normal and/or abiotic stresses. Taken together, the results suggest that the transcription factor SlHB2 acts as a negative regulator in the drought and high-salinity stress signaling pathways.