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 in 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 compared with Arabidopsis thaliana GDSL esterases/lipases 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 11 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 GDSLs in watermelon were highly homologous to those in Arabidopsis thaliana, melon and cucumber. Transcriptome analyses showed the tissue-specific and common expression of the GDSL genes in leaf and root tissues and identified nitrogen-related genes under low nitrogen (N) stress compared with optimal N conditions.
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.