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Members of the zinc-finger homeodomain (ZF-HD) family play a key role in the control of plant growth and development, which are involved in plant responses to stress. Although many functional studies of this gene family have been performed in different plants, the features of this family in tomato (Solanum lycopersicum) remain unknown. In this study, we identified 22 ZF-HD genes in the tomato genome and classified them into seven groups located on six chromosomes. Expression of 15 ZF-HD genes in tomato was studied in different tissues to identify their putative functions in many aspects of plant growth and development. Based on previous phylogenetic analyses in arabidopsis (Arabidopsis thaliana), our results showed that some tomato SL-ZH (S. lycopersicum zinc-finger homeodomain) genes cluster into the same neighbor-joining (NJ) branch as arabidopsis, indicating that these genes may share similar structures and functions in these plants. Gene expression analysis demonstrated that the tomato ZF-HD gene may be involved in abiotic stress responses, the SL-ZH13 gene in cold stress and the SL-ZH15 gene in drought stress; almost all tomato ZF-HD genes were responsive to salt stress, except for SL-ZH7, -ZH8, and -ZH22. However, the structures and functions of unknown groups require further research. In conclusion, this study identified tomato ZF-HD genes and analyzed their gene structures, subfamily distribution, and expression characteristics. These experiments combined with previous research findings reveal significant information and insight for future studies on the agronomic features and stress resistance in tomato.

BRI1-EMS-suppressor 1 (BES1) is a transcription factor (TF) that functions as a master regulator of brassinosteroid (BR)-regulated gene expression. Here, we provide a complete overview of Solanum lycopersicum BES1 (SLB) genes, including phylogeny, gene structure, protein motifs, chromosome locations and expression characteristics. Through bioinformatic analysis, we compared the sequences of SLB genes, arabidopsis (Arabidopsis thaliana) genes, and chinese cabbage (Brassica pekinensis) genes. All of the gene sequences were divided into three groups by cluster analysis. SLB genes were mapped to the eight tomato (S. lycopersicum) chromosomes. Bioinformatic analysis showed that SLB genes shares similarities with the proteins from other plants, though different species exhibit specific features. The expression patterns of SLB genes in various tissues and under different abiotic conditions were analyzed by quantitative reverse transcription polymerase chain reaction. SLB genes were found to be induced by multiple stresses, particularly salt stress, indicating that SLB genes may have important roles in the response to unfavorable environmental changes. This study provides insight into the evolution of SLB genes and may aid in the further functional identification of BES1 proteins and the response of tomato plants to different stresses.

Zinc finger-homeodomains (ZF-HDs) are considered transcription factors that are involved in a variety of life activities in plants, but their function in regulating plant salt stress tolerance is unclear. The SL-ZH13 gene is significantly upregulated under salt stress treatment in tomato (Solanum lycopersicum) leaves, per our previous study. In this study, to further understand the role that the SL-ZH13 gene played in the response process of tomato plants under salt stress, the virus-induced gene silencing (VIGS) method was applied to down-regulate SL-ZH13 expression in tomato plants, and these plants were treated with salt stress to analyze the changes in salt tolerance. The silencing efficiency of SL-ZH13 was confirmed by quantitative real-time PCR analysis. SL-ZH13-silenced plants wilted faster and sooner than control plants under the same salt stress treatment condition, and the main stem bending angle of SL-ZH13-silenced plants was smaller than that of control plants. Physiological analysis showed that the activities of superoxide dismutase, peroxidase, and proline content in SL-ZH13-silenced plants were lower than those in control plants at 1.5 and 3 hours after salt stress treatment. The malondialdehyde content of SL-ZH13-silenced plants was higher than that in control plants at 1.5 and 3 hours after salt stress treatment; H₂O₂ and O₂ ^- accumulated much more in leaves of SL-ZH13-silenced plants than in leaves of control plants. These results suggested that silencing of the SL-ZH13 gene affected the response of tomato plants to salt stress and decreased the salt stress tolerance of tomato plants.