Leucine-Rich Repeat Extension 7 Gene Confers Cotton Resistance to Verticillium Wilt

Leucine-rich repeat extensins (LRXs) are essential regulators of plant development, cell wall integrity, and stress responses. However, genome-wide LRX studies in cotton are limited. Analysis of four Gossypium species identified 29, 28, 16, and 16 LRX genes in G. hirsutum, G. barbadense, G. arboreum, and G. raimondii, respectively. Phylogenetic analysis resolved these 89 genes into four subfamilies (I-IV). Structural annotation revealed that cotton LRX family members exhibit conserved domain architectures. This finding was corroborated by motif analysis, which revealed notable conservation in the motif compositions of most cotton LRX proteins, suggesting functional conservation across evolutionary lineages. Distinct spatiotemporal expression patterns were uncovered between G. hirsutum and G. barbadense. Prolonged exposure to extreme temperatures induced widespread down-regulation of most GhLRX genes, whereas genes in subgroup IV were significantly up-regulated under salt and drought stress conditions, respectively. Notably, GhLRX7 showed a more proactive responding profile to Verticillium wilt (VW) infection, which was therefore selected for functional validation employing virus-induced gene silencing in the cotton cultivars MBI9626 and CCRI36. Phenotypic analysis of silenced plants revealed exacerbated disease symptoms compared to wild-type controls, providing direct evidence implicating GhLRX7 as a key contributor to defense against VW.