Overexpression of Gossypium arboreum 3-ketoacyl-CoA synthase 6 (GaKCS6) gene enhanced leaf epicuticle wax in Gossypium hirsutum L. and improved tolerance against whitefly

Abstract

Cotton Leaf Curl Virus (CLCuV) is a significant threat to cotton production, as it causes Cotton Leaf Curl Disease (CLCuD). Whitefly serves as a vector for the transmission of this virus. It can be controlled by developing barriers against whitefly infestation. The leaf epicuticle wax acts as a protective barrier against whitefly attacks. Research into wax biosynthesis and the fatty acid elongation pathway has highlighted the role of the 3-ketoacyl-CoA synthase (KCS) gene family in producing very-long-chain fatty acids (VLCFAs) in plants. The 3-ketoacyl-CoA synthase 6 (GaKCS6) gene, isolated from the CLCuV-resistant FDH-170 variety of Gossypium arboreum, was cloned under the control of the CaMV35S constitutive promoter and transformed into the CLCuV-susceptible Gossypium hirsutum variety CKC-3 resulting in significantly higher leaf epicuticle wax deposition. Overexpression of GaKCS6 in the transgenic cotton plants was confirmed through quantitative real-time PCR. The transgenic plants not only exhibited average growth but also showed improvements in agronomic traits. Scanning Electron Microscope (SEM) analysis further validated the enhanced leaf epicuticle wax deposition in transgenic plants compared to non-transgenic (control). A free-choice bioassay against whiteflies demonstrated that the transgenic plants remained free of viral infection, as confirmed by real-time PCR. These findings indicate that increased leaf epicuticle wax deposition in transgenic cotton effectively prevents whitefly attacks and the transmission of CLCuV. It suggests that the GaKCS6 gene plays a crucial role in producing leaf epicuticle wax through the VLCFAs biosynthesis pathway.