Comprehensive Genomic Characterization and Expression Analysis of the Lipoxygenase Gene Family in Watermelon under Hormonal Treatments

Abstract

Lipoxygenases (LOXs) are non-haem iron-containing dioxygenases and play vital roles in a variety of plant biological processes. Here, we first carried out the genome-wide identification of LOX genes in watermelon. A total of 16 LOX genes were identified, which could be classified into two categories according to phylogenetic analysis: the 9-LOXs (ClLOX1–4, 12, and 15) and 13-LOXs (ClLOX5–11, 13, 14, and 16). Furthermore, the protein structures, intrachromosomal distributions, and gene structures were thoroughly analyzed. Cis-element analysis of the promoter regions indicated that the expression of ClLOX genes may be influenced by stress and plant hormones. Bioinformatic and expression analyses revealed that the expression of ClLOX genes is tissue-specific and hormone-responsive. The detected LOX genes exhibited distinctive expression patterns in various tissues. Different ClLOX genes showed different responses to methyl jasmonate (MeJA), salicylic acid (SA), and ethylene (ET) treatments, particularly ClLOX7, which exhibited the most active response to the above treatments. This study provides valuable information for a better understanding of the functions of LOX genes and further exploration of the LOX gene family in watermelon.