A SNP Mutation in Homeodomain-DDT (HD-DDT) Transcription Factor Results in () in Cucumber ( L.).

Trichome is a natural physical barrier protecting plants against environmental stresses, natural infestations, ultraviolet rays and pathogenicity. Trichome also helps plants in maintaining appropriate water content by reducing transpiration rate. The molecular mechanism regulating unicellular trichome development in Arabidopsis has been extensively elucidated, but the molecular mechanism regulating multicellular trichome development remains unclear. In this study, we identified a () mutant from a cucumber EMS (Ethylmethylsulfone) mutagenesis population. Genetic analysis indicated that an incomplete dominant gene controls the trait. Using a combination of map-based cloning and BSA-seq (Bulked Segregant Analysis -Sequencing), we identified the candidate gene, , responsible for the mutation. Sequence alignment revealed one base substitution in gene , resulting in an amino acid substitution. The deduced amino acid sequence of encodes a HD-DDT (homeodomain-DDT) transcriptional regulatory protein containing a conserved homeobox domain and a DDT domain. Gene expression analysis revealed that the expression level of in the mutant was similar to that in the WT (wild type). Transcriptome analysis indicated that the gene may regulate the development of the epidermis by influencing plant hormone signaling pathways or participating in several transcription factor pathways. The results of this study are fundamental for a better understanding of the function of the HD-DDT transcription factor in the trichome development of cucumber.