Genome-wide identification and expression analysis of the lipoxygenase gene family in sesame reveals regulatory networks in response to abiotic stress.

Abstract

Background: Plant lipoxygenase (Lox) genes, catalyze polyunsaturated fatty acids and play essential roles in plant growth, development, and stress responses. It is extensively studied under various stresses, their role in abiotic stress responses remains unexplored in sesame.

Methods and results: This study identified seven Lox genes in sesame divided into two subfamilies: 9-Lox (Silox1, Silox2 and Silox3) are likely involved in pathogen defence and signalling and 13-Lox (Type-I: Silox4 and Type-II: Silox5, Silox6 and Silox7) play crucial roles in jasmonic acid biosynthesis and abiotic stress responses. Silox genes have undergone purifying selection, promoting the stability of gene function and prefer codons with A or T in the third position. The chromosomal distribution, sequence similarity, and subcellular localization, with conserved lipoxygenase domains and motifs were analysed. Promoter regions contained 34 cis-acting regulatory elements (e.g. WRKY, ERF, and bHLH) and 35 transcription factors binding sites (TFBS) linked to light, stress (e.g. MYC, W-box, ERE and STRE), phytohormones, and growth. Differential Gene Expression (DGE) analysis showed Lox1 was upregulated in Drought sensitive (DS) and in Drought tolerant (DT) the Lox1 & Lox3 were upregulated when compared to control. In addition, weighted gene co-expression network analysis (WGCNA) of Lox, showed that blue module is positively correlated with drought tolerance. Fourteen hub genes related to stress were identified, which closely associated with Lox1. Gene ontology and KEGG pathway analyses showed that these genes were linked to linoleic acid metabolism, lipid metabolism, and stress response. Quantitative Real-Time PCR (qRT-PCR) analysis confirmed that Silox genes showed time-varying differential expression under drought, salt and a combined drought-salt stress treatments.

Conclusion: This research lays the groundwork for future studies on the role of Lox genes in sesame's growth and stress adaptation.