Genome-wide identification of LOX gene in four cotton species and revealed its function in callus induction and drought tolerance

Abstract

Cotton is one of the important fiber crops. Drought is the primary abiotic factor that restricts cotton growth and development and lowers its output. Plant LOX (lipoxygenases) genes catalyze the oxidation of polyunsaturated fatty acids into a variety of functional oxylipins. The LOX gene family has been thoroughly investigated under biotic and abiotic stressors; however, knowledge of their functions on callus induction and regeneration in cotton is still scarce. This study identified 34, 38, 23, and 20 LOX genes in the Gossypium hirsutum, Gossypium barbadense, Gossypium arboreum, and Gossypium raimondii, respectively. The LOX genes were found to be divided into three main categories, 9-LOX, 13-LOX Type I, and 13-LOX Type II. Three accessions of G. hirsutum were used to generate callus from hypocotyl, cotyledon, and shoot tip and we observed that the highest expression of the GhLOX genes were in the hypocotyl callus and most of LOX gene expression was up-regulated in one week callus and decreased in two week and four week callus except in the shoot tip induced callus in Jinmian 498. Virus-induced gene silencing of GhLOX5 (Gh_A02G037000) revealed that the growth of the silenced plant was significantly decreased compared to WT. Excised leaf water loss and relative electrolyte leakage levels were increased about 23 % and 12 % in the GhLOX5 silenced plant when compared to the WT. Compared to the WT, the silenced plant had significantly higher antioxidant activity (25 % in MDA content and 45 % in H₂O₂ content). The importance of LOX genes in drought stress and callus induction is clear, but further research is needed to understand their molecular mechanism.