Identification, Evolution, and Expression Analysis of Ten Gene Families of General Phenylpropanoid and Monolignol-Specific Metabolism in Cucumber.

As the main component of secondary thickened plant cell walls, lignin plays a crucial role in plant development and protection from biotic and abiotic stressors. The lignin biosynthesis pathway has not been extensively studied in cucumber, an important vegetable cultivated worldwide. Therefore, this study identified and characterised the family members of general phenylpropanoid and monolignol-specific metabolism in cucumber. We identified 10 gene families comprising 84 enzyme genes distributed across 7 chromosomes. Phylogenetic, collinearity, and motif analyses revealed significant conservation of family members among different species. Furthermore, expression analysis was performed using transcriptome data and qRT-PCR. These genes exhibited organ-specific expression patterns, and their expression occurred in response to biotic and abiotic stress. Subcellular localisation experiments indicated that CsHCT12 and CsCAD2 were localised in the cytoplasm and the plasma membrane. Furthermore, potential miRNA-targeted analysis identified 84 family genes in cucumber that could be regulated by 403 miRNAs. The transcription factor (TF) regulatory network revealed 118 TFs that may regulate 78 family genes. Luciferase assays have indicated that CsWRKY50 can activate the expression of CsPAL12 and Cs4CL10. These findings lay the foundation for further exploration of the functional roles of gene family members of the general phenylpropanoid and monolignol-specific metabolism in cucumber.