Mechanismal analysis of resistance to Verticillium dahliae in upland cotton conferred by overexpression of RPL18A-6 (Ribosomal Protein L18A-6)

Verticillium wilt of cotton, caused by the fungal phytopathogen Verticillium dahliae (V. dahliae), is one of the most devastating diseases of upland cotton. While Verticillium dahliae-resistant phenotypes have been identified in several plant species, the underlying mechanisms of resistance need further clarification. Here, the induction of resistance to V. dahliae through over-expression of the GhARPL18A-6 (Ribosomal protein L18A) in Gossypium hirsutum (G. hirsutum) was demonstrated. GhARPL18A-6 was highly induced in G. hirsutum acc. Zhongzhimian2 (Zz2) after inoculation with Verticillium dahliae. Knock-down of GhARPL18A-6 in Zz2 led to disease-sensitive phenotypes to V. dahliae. Further studies showed that increased lignin deposition, an enhanced reactive oxygen species (ROS) burst, and phenylpropanoid biosynthesis defense response pathways all contributed to a decrease in colonization by V. dahliae. RNA-seq analysis of GhARPL18A-6 over-expression and wild-type cotton revealed differentiate-expression of cell wall biosynthesis, sucrose signaling and metabolism, lignin biosynthesis, and ROS response genes in resistant plants inoculated with V. dahliae. Given the susceptibility of most commercially valuable cotton lines, this research provides insight into the mechanisms of resistance to Verticillium wilt as well as novel germplasm for cotton breeding.