AUTHOR=Li Haipeng , Zhang Shulin , Zhao Yunlei , Zhao Xulong , Xie Wenfei , Guo Yutao , Wang Yujie , Li Kun , Guo Jinggong , Zhu Qian-Hao , Zhang Xuebin , Jia Kun-Peng , Miao Yuchen 

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

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.840397

DOI=10.3389/fpls.2022.840397

ISSN=1664-462X

ABSTRACT=<p>Verticillium wilt, caused by the soil-borne fungus <italic>Verticillium dahliae</italic>, is one of the most devastating diseases in cotton (<italic>Gossypium</italic> 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, <italic>p</italic>-coumaryl- (H), coniferyl- (G), and sinapyl-alcohols (S), which are the fundamental blocks of lignin. Here, we identified <italic>CAD</italic> genes in <italic>G. hirsutum</italic>, analyzed their expression profiles in cotton leaf, stem, and root from different developmental stages, and selected <italic>GhCAD35</italic>, <italic>GhCAD45</italic>, and <italic>GhCAD43</italic>, which were consistently induced by <italic>V. dahliae</italic> inoculation in <italic>G. hirsutum</italic> cultivars resistant or susceptible to <italic>V. dahliae</italic>. On the basis of confirmation of the <italic>in vitro</italic> 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 <italic>GhCAD35</italic>, <italic>GhCAD45</italic>, or <italic>GhCAD43</italic> on resistance to <italic>V. dahliae</italic> as well as on deposition and the composition of lignin. Silencing each of the three <italic>CAD</italic>s impaired the defense-induced lignification and salicylic acid biosynthesis in stem, and compromised resistance to <italic>V. dahliae</italic>. Moreover, our study showed that silencing the three <italic>GhCAD</italic>s severely affected the biosynthesis of S-lignin, leading to a decrease of the syringyl/guaiacyl (S/G) ratio. Heterogeneous overexpression of <italic>GhCAD35</italic>, <italic>GhCAD45</italic>, or <italic>GhCAD43</italic> in <italic>Arabidopsis</italic> enhanced disease resistance. Taken together, our study demonstrates a role of the three <italic>GhCAD</italic>s in defense-induced lignin biosynthesis and resistance to <italic>V. dahliae</italic> in <italic>G. hirsutum</italic>.</p>