Genome-Wide Identification and Expression Profiling of Gene Family in Passion Fruit () Under and Drought Stress Conditions.

Plant and fruit surfaces are covered with cuticle wax and provide a protective barrier against biotic and abiotic stresses. Cuticle wax consists of very-long-chain fatty acids (VLCFAs) and their derivatives. β-Ketoacyl-CoA synthase () is a key enzyme in the synthesis of VLCFAs and provides a precursor for the synthesis of cuticle wax, but the gene family was yet to be reported in the passion fruit (). In this study, thirty-two genes were identified in the passion fruit genome and phylogenetically grouped as -like, -like, -like, and -like. Furthermore, thirty-one genes were positioned on seven chromosomes, while one was localized to the unassembled genomic scaffold. The -element analysis provides insight into the possible role of genes in phytohormones and stress responses. Syntenic analysis revealed that gene duplication played a crucial role in the expansion of the gene family and underwent a strong purifying selection. All PeKCS proteins shared similar 3D structures, and a protein-protein interaction network was predicted with known proteins. There were twenty putative ped-miRNAs which were also predicted that belong to nine families targeting thirteen genes. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation results were highly associated with fatty acid synthase and elongase activity, lipid metabolism, stress responses, and plant-pathogen interaction. The highly enriched transcription factors (TFs) including ERF, MYB, Dof, C2H2, TCP, LBD, NAC, and bHLH were predicted in genes. qRT-PCR expression analysis revealed that most genes were highly upregulated in leaves including , and but not in stem and roots tissues under drought stress conditions compared with controls. Notably, most genes were upregulated at 9th dpi under biotic stress condition compared to controls. This study provides a basis for further understanding the functions of genes, improving wax and VLCFA biosynthesis, and improvement of passion fruit resistance.