Genome-wide identification and functional analysis of lipoxygenase (LOX) gene family in some Fabaceae species using bioinformatics methods

Lipoxygenases (LOXs) are non-heme iron-containing dioxygenases involved in the apoptotic (programmed cell death) pathway and biotic and abiotic stress responses in plants. In the present study, we identified 95 LOX homologous genes from four Fabaceae species (Cicer arietinum, Glycine max, Phaseolus vulgaris, Medicago truncatula), which could be divided into 9-LOX, 13-LOX type I, and type II subgroups according to their phylogenetic relationships with Arabidopsis, rice, barley, and foxtail millet. LOX genes are distributed unevenly across the chromosomes, and their coding enzyme is active in the cytoplasm and chloroplast. These genes are intron rich, have six to nine introns, and are conserved in gene structure and intron phase. All identified genes have the conserved lipoxygenase and PLAT/LH2 domains. Several cis-acting elements related to hormones and stresses, such as ERE, MYB, and MYC in the LOXs promoters, indicated the role of these genes in plant development and responses to environmental stresses. In addition, different miRNA molecules were identified that regulate the post-transcriptional expression of LOXs genes through cleavage or inhibition of translation. Transcriptome data-based gene expression analysis showed that Glycine max LOXs expression pattern differed under abiotic stress conditions, and GmLOX4, GmLOX21, GmLOX25, GmLOX5, GmLOX22, GmLOX24, GmLOX14, GmLOX16, GmLOX7, and GmLOX26 were highly expressed in response to salt, drought, cold and heat stresses, indicating that they can improve the tolerance of Glycine max to abiotic stress. This study provides valuable information for a better understanding of the function of LOX genes and further exploration of the LOX gene family in Fabaceae.