Identification and Characterization of Cinnamyl Alcohol Dehydrogenase Encoding Genes Involved in Lignin Biosynthesis and Resistance to Verticillium dahliae in Upland Cotton (Gossypium hirsutum L.)

Abstract

Verticillium wilt, caused by the soil-borne fungus Verticillium dahliae, is one of the most devastating diseases in cotton (Gossypium spp.). Lignin in the cell wall forms a physical barrier to inhibit pathogen invasion, and defense-induced lignification reinforces secondary cell wall to prevent pathogens from further spreading. Cinnamyl alcohol dehydrogenases (CADs) catalyze the production of three main monolignols, p-coumaryl- (H), coniferyl- (G), and sinapyl-alcohols (S), which are the fundamental blocks of lignin. Here, we identified CAD genes in G. hirsutum, analyzed their expression profiles in cotton leaf, stem, and root from different developmental stages, and selected GhCAD35, GhCAD45, and GhCAD43, which were consistently induced by V. dahliae inoculation in G. hirsutum cultivars resistant or susceptible to V. dahliae. On the basis of confirmation of the in vitro enzymatic activity of the three proteins in generation of the three monolignols, we used virus-induced gene silencing (VIGS) to investigate the effects of silencing of GhCAD35, GhCAD45, or GhCAD43 on resistance to V. dahliae as well as on deposition and the composition of lignin. Silencing each of the three CADs impaired the defense-induced lignification and salicylic acid biosynthesis in stem, and compromised resistance to V. dahliae. Moreover, our study showed that silencing the three GhCADs severely affected the biosynthesis of S-lignin, leading to a decrease of the syringyl/guaiacyl (S/G) ratio. Heterogeneous overexpression of GhCAD35, GhCAD45, or GhCAD43 in Arabidopsis enhanced disease resistance. Taken together, our study demonstrates a role of the three GhCADs in defense-induced lignin biosynthesis and resistance to V. dahliae in G. hirsutum.

Comparative transcriptome profiling and co-expression network analysis uncover the key genes associated with pear petal defense responses against Monilinia laxa infection

“…In our study, JA was also highlighted as the principal phytohormone in signaling transduction-mediated responses in Sissy based on the S48 group, as a lipoxygenase gene, which is related to JA biosynthesis, and was upregulated at 48 HAI. In this line, the activation of a CAD gene might also contribute to the elevated tolerance of the Sissy cultivar, as such genes are involved in lignin biosynthesis and resistance to pathogens ( Li et al., 2022 ). In addition, one PAL - encoding gene, the key enzyme in the phenol biosynthesis pathway, was found upregulated in the S48 group, whereas its triggering is likely correlated with the Sissy higher competence to block M. laxa growth.…”

“…This supports further our results, as the main hub gene in the regulatory network of the Sissy 48 HAI-related module was a cytokinin dehydrogenase 7-encoding gene. Such cytokinin-related genes have been reported to support plant responses and resistance to necrotrophic pathogens ( Li et al., 2022 ; Zhu et al., 2022 ).…”