Molecular mechanism analysis of watermelon ClSRP54 gene regulating plant height
In the preliminary stage of this study, a mutant PKH352 with yellowed leaves and dwarf plant height was screened from a watermelon EMS mutant library, and its candidate gene was identified as ClSRP54 (Clygp). Subsequently, homozygous edited plants of the ClSRP54 gene were obtained via CRISPR/Cas9-mediated knockout. Phenotypic observation revealed that the gene-edited plants exhibited consistent phenotypes with the mutant, including leaf yellowing and reduced plant height. Building on this foundation, the present study investigated the molecular mechanism underlying ClSRP54 mediated regulation of watermelon plant height. Phenotypic characterization, cytological observations, and transcriptome analysis were performed on the vines of the transgenic CR-ClSRP54 plants and wild-type YL plants. The results demonstrated that the internode length and plant height of CR-ClSRP54 were significantly reduced; the longitudinal cell area of the stems was remarkably smaller. Transcriptome sequencing of the second internode (from top to bottom) of CR-ClSRP54 and YL identified 1030 differentially expressed genes (DEGs), among which 857 were upregulated and 173 were downregulated. Functional enrichment analysis indicated that the majority of DEGs were enriched in pathways related to plant hormone synthesis, metabolism, and signal transduction. Collectively, these findings suggest that ClSRP54 may regulate watermelon plant height through the synergistic action of multiple plant hormones. This study enriches the molecular regulatory network of watermelon plant height and provides a theoretical basis for plant type breeding in cucurbit crops.