Downregulation of SL-ZH13 transcription factor gene expression decreases drought tolerance of tomato

Zinc finger-homeodomain proteins (ZF-HDs) are transcription factors that regulate plant growth, development, and abiotic stress tolerance. The SL-ZH13 gene was found to be significantly upregulated under drought stress treatment in tomato (Solanum lycopersicum) leaves in our previous study. In this study, to further understand the role that the SL-ZH13 gene plays in the response of tomato plants to drought stress, the virus-induced gene silencing (VIGS) method was applied to downregulate SL-ZH13 expression in tomato plants, and these plants were treated with drought stress to analyze the changes in drought tolerance. The SL-ZH13 silencing efficiency was confirmed by quantitative real-time PCR (qRT-PCR) analysis. In SL-ZH13-silenced plants, the stems wilted faster, leaf shrinkage was more severe than in control plants under the same drought stress treatment conditions, and the mean stem bending angle of SL-ZH13-silenced plants was smaller than that of control plants. Physiological analyses showed that the activity of superoxide dismutase (SOD) and peroxidase (POD) and the content of proline (Pro) in SL-ZH13-silenced plants were lower than those in control plants after 1.5 and 3 h of drought stress treatment. The malondialdehyde (MDA) content in SL-ZH13-silenced plants was higher than that in control plants after 1.5 and 3 h of drought stress treatment, and H2O2 and O-2(-)center dot accumulated much more in the leaves of SL-ZH13-silenced plants than in the leaves of control plants. These results suggested that silencing the SL-ZH13 gene affected the response of tomato plants to drought stress and decreased the drought tolerance of tomato plants.