GhCCR24 mediates lignin deposition in cell wall to enhance salt tolerance in cotton

Soil salinization poses a significant threat to global cotton production. Enhancing salt tolerance in cotton requires a deep understanding of its underlying molecular mechanisms. Lignin, a crucial component of the plant cell wall, plays a vital role in stress adaptation, with Cinnamoyl-CoA Reductase (CCR) serving as the key rate-limiting enzyme in its biosynthesis. However, the function of CCR genes in cotton remains largely unexplored. Here, we conducted a genome-wide analysis and identified 34 CCR genes in Gossypium hirsutum. Among them, GhCCR24 was highly induced by salt stress, particularly in roots. Virus-induced gene silencing (VIGS) of GhCCR24 resulted in compromised plant growth, reduced lignin deposition, and thinner secondary cell walls. Under salt stress, GhCCR24-silenced plants exhibited severe oxidative damage, ion homeostasis disruption (elevated Na⁺ / K⁺ ratio), and a significant decline in salt tolerance. Our findings demonstrate that GhCCR24 acts as a core positive regulator of cotton's response to salt stress by mediating lignin biosynthesis, which reinforces cell walls and thereby maintains ion and oxidative homeostasis. This study provides a valuable gene resource for the genetic improvement of salt-tolerant cotton.