Genome-Wide Analysis and Expression Profiling of Watermelon <i>VQ</i> Motif-Containing Genes Under Abiotic and Biotic Stresses
2025
Yanjun He | Jia Shen | Xinyang Xu | Weisong Shou
Valine-glutamine (VQ) motif-containing proteins play important roles in diverse plant developmental processes and signal transduction in response to biotic and abiotic stresses. However, no systematic investigation has been conducted on <i>VQ</i> genes in watermelon. In this study, we identified 31 watermelon <i>VQ</i> genes, which were classified into six subfamilies (I–VI). All of the deduced proteins contained a conserved FxxxVQxL/F/VTG motif. Eleven <i>ClVQs</i> were involved in segment duplication, which was the main factor in the expansion of the VQ family in watermelon. Numerous stress- and hormone-responsive <i>cis</i>-elements were detected in the putative promoter region of the <i>ClVQ</i> genes. Green fluorescent protein fusion proteins for ten selected ClVQs were localized in the nucleus, but three ClVQs also showed signals in cell membranes and the cell wall, thus confirming their predicted divergent functionality. Quantitative real-time PCR (qRT-PCR) analysis indicated that the majority of <i>ClVQ</i> genes were specifically or preferentially expressed in certain tissues or organs, especially in the male flower. Analyses of RNA-sequencing data under osmotic, cold, and drought stresses and <i>Cucumber green mottle mosaic virus</i> (CGMMV) infection revealed that the majority of <i>ClVQ</i> genes, especially those from subfamily IV, were responsive to these stresses. The results provide useful information for the functional characterization of watermelon <i>ClVQ</i> genes to unravel their biological roles.
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