Laccase gene, GhLAC15, enhanced Verticillium wilt resistance via increasing defense-induced lignification and arabinose and xylose accumulation in the cell wall of Gossypium hirsutum

Working group session: 
Structural Genomics
Presentation type: 
5 minute Oral and Poster
Authors: 
Zhang,Yan
Wu,Lizhu
Wang,XIngfen
Li,Zhikun
Wang,Guoning
Yan,Yuanyuan
Wu,Jinhua
Wu,Liqiang
Zhang,Guiyin
Ma,Zhi-ying
Author Affliation: 
College of Agronomy,Hebei Agricultural University
College of Agronomy,Hebei Agricultural University
College of Agronomy,Hebei Agricultural University
College of Agronomy,Hebei Agricultural University
College of Agronomy,Hebei Agricultural University
College of Agronomy,Hebei Agricultural University
College of Agronomy,Hebei Agricultural University
College of Agronomy,Hebei Agricultural University
College of Agronomy,Hebei Agricultural University
College of Agronomy,Hebei Agricultural University
Abstract: 
Laccase gene, GhLAC15, enhanced Verticillium wilt resistance via increasing defense-induced lignification and arabinose and xylose accumulation in the cell wall of Gossypium hirsutum YanZhang#, Li-zhuWu#, Xing-fenWang, Zhi-kun Li, Jun Yang, Guo-ningWang, Yuan-yuanYan, Jin-huaWu, Li-qiangWu, Gui-yinZhang, Zhi-yingMa* College of Agronomy, North China Key Laboratory for Crop Germplasm Resources of Education Ministry, Co-Innovation Center For Cotton Industry of Hebei Province, Hebei Agricultural University, Baoding 071001, China. #These authors contributed equally to this work. *Correspondence: mzhy@hebau.edu.cn Tel: +86-312-7528401 Fax: +86-312-7521279 Verticillium dahliae is a phytopathogenic fungal pathogen that causes vascular wilt diseases responsible for considerable decreases in cotton yields. Enhancing the immune system of plants is regarded as useful for controlling this disease. Lignification of cell wall appositions is a conserved basal defense mechanism in plant innate immune response. Significant roles of laccase family in cotton fiber development had been reported. However, the function of laccase involved in defense-induced lignification has not been described to date. During screening the SSH library of resistant cultivar Jimian20 inoculated by V. dahliae, a laccase gene displayed strongly induced by the pathogen, which was phylogenetically related to AtLAC15 gene, containing conserved domains that laccase commonly possessed, thus named it as GhLAC15. Overexpression GhLAC15 gene in Arabidopsis enhanced cell wall lignification, resulting in increasing the total lignin and G monolignol as well as the radio of G/S, which significantly improved the Verticillium wilt resistance of transgenic plants. In addition, the predominant carbohydrate constituents of cell wall, arabinose (Ara), xylose (Xyl) and glucose (Glc), displayed obvious difference between transgenic plants and wild type. The levels of Ara and Xyl distinctly increased, whereas the Glc level decreased in transgenic Arabidopsis. Based on the high levels of Ara and Xyl representing a high content of arabinose-substituted xylan (arabinoxylan) in enhancing plant resistance to pathogen, the high levels of Ara and Xyl provided the biochemical evidence in defense against V. dahliae in our transgenic Arabidopsis. Furthermore, suppressing the transcriptional level of GhLAC15, via virus-induced gene silencing, resulted in the increase of diseased plant rate and disease index in cotton. More fungal colonies were found in the roots of silent plants, suggesting that the extent of fungal colonization in silent plants was much more severe than in control plants. The content of monolignol and the G/S radio also decreased in the silent cotton plants, which led to resistant cotton cv. Jimian20 susceptible to the disease. These results demonstrated that GhLAC15 gene enhanced Verticillium wilt resistance via increasing defense-induced lignification and arabinose and xylose accumulation in the cell wall of G. hirsutum. This broadens our knowledge in defense-induced lignifications and cell wall modification as a defense mechanism against V. dahliae.