AUTHOR=Rizwan Hafiz Muhammad , Shaozhong Fang , Li Xiaoting , Bilal Arshad Muhammad , Yousef Ahmed Fathy , Chenglong Yang , Shi Meng , Jaber Mohammed Y. M. , Anwar Muhammad , Hu Shuai-Ya , Yang Qiang , Sun Kaiwei , Ahmed Mohamed A. A. , Min Zheng , Oelmüller Ralf , Zhimin Lin , Chen Faxing 

TITLE=Genome-Wide Identification and Expression Profiling of KCS Gene Family in Passion Fruit (Passiflora edulis) Under Fusarium kyushuense and Drought Stress Conditions

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.872263

DOI=10.3389/fpls.2022.872263

ISSN=1664-462X

ABSTRACT=<p>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 (<italic>KCS</italic>) is a key enzyme in the synthesis of VLCFAs and provides a precursor for the synthesis of cuticle wax, but the <italic>KCS</italic> gene family was yet to be reported in the passion fruit (<italic>Passiflora edulis</italic>). In this study, thirty-two <italic>KCS</italic> genes were identified in the passion fruit genome and phylogenetically grouped as <italic>KCS1</italic>-like, <italic>FAE1</italic>-like, <italic>FDH</italic>-like, and <italic>CER6</italic>-like. Furthermore, thirty-one <italic>PeKCS</italic> genes were positioned on seven chromosomes, while one <italic>PeKCS</italic> was localized to the unassembled genomic scaffold. The <italic>cis</italic>-element analysis provides insight into the possible role of <italic>PeKCS</italic> genes in phytohormones and stress responses. Syntenic analysis revealed that gene duplication played a crucial role in the expansion of the <italic>PeKCS</italic> 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 <italic>Arabidopsis</italic> proteins. There were twenty putative ped-miRNAs which were also predicted that belong to nine families targeting thirteen <italic>PeKCS</italic> 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 <italic>PeKCS</italic> genes. qRT-PCR expression analysis revealed that most <italic>PeKCS</italic> genes were highly upregulated in leaves including <italic>PeKCS2, PeKCS4, PeKCS8, PeKCS13</italic>, and <italic>PeKCS9</italic> but not in stem and roots tissues under drought stress conditions compared with controls. Notably, most <italic>PeKCS</italic> genes were upregulated at 9th dpi under <italic>Fusarium kyushuense</italic> biotic stress condition compared to controls. This study provides a basis for further understanding the functions of <italic>KCS</italic> genes, improving wax and VLCFA biosynthesis, and improvement of passion fruit resistance.</p>