Genome-wide identification and analysis of promising GDSL-type lipases related to gummy stem blight resistance in watermelon (Citrullus lanatus)

Abstract

The GDSL esterase and lipase families play important roles in abiotic stress, pathogen defense, seed development and lipid metabolism. Identifying the lipase activity of a putative GDSL lipase is necessary to determine its function. Systematic analysis of the GDSL gene family is still lacking for Citrullus lanatus. In this study, we identified 65 watermelon GDSL-type esterase/lipase genes and divided these genes into 6 clades based on phylogeny. The phylogenetic relationship of watermelon GDSL genes and Arabidopsis thaliana GDSL esterase/lipase genes was also determined, and these genes were divided into four groups related to morphological development, abiotic stress response, pathogen defense, and secondary metabolism. The chromosomal location of these genes revealed that they are distributed unevenly across all eleven watermelon chromosomes. Analysis of duplication events suggested that segmental duplication and tandem duplication were the major driving forces of GDSL family evolution. Synteny analysis indicated that GDSL genes in watermelon were highly homologous to those in A. thaliana, melon and cucumber. Transcriptome analyses showed the organ-specific and common expression of the GDSL genes in the root, stem and leaf organs and revealed that some of the GDSL genes are responsive to gummy stem blight inoculation, suggesting the possible involvement of these genes in disease stress–response pathways. Our results provide a basis for selecting candidate watermelon GDSL genes for further studies to determine the biological functions of the GDSL genes in watermelon.