An LRR-TM gene in Dt09 confers Verticillium wilt resistance by activating SA signaling in cotton

Verticillium wilt, caused by soil-borne fungus Verticillium dahliae, is one of the most destructive diseases in cotton. An LRR-TM gene we cloned from Gossypium barbadense (GbVe) significantly improved Verticillium wilt resistance of transgenic Arabidopsis. However, the resistance mechanism of the GbVe is still obscure. In the present study, we identified that the GbVe located in Dt09, homologous to tomato Ve1 but possessing lower identity with other reported cotton Ve genes in At01 and /or Dt01, and further investigated the molecular mechanism of the gene in resistance against V. dahliae. Ectopic expression of GbVe activated salicylic acid signaling, elevating the expression levels of EDS1, NDR1, PR4 and PR5 in transgenic Arobidopsis plants, and enhanced the accumulation of lignin, which improved resistance to V. dahliae. These results provide us important clue to further investigate the molecular mechanism of GbVe in cotton itself. Overexpression of GbVe in cotton (G. hirsutum) made defense response to Verticillium wilt enhanced. Transgenic cotton led to activation of SA signaling pathway (including cotton ICS1, EDS1, NPR1, NDR1, PR1, PR4 and PR5 genes), causing SA acumulation and lignin increase that confer resistance to V. dahliae. We also detected that the GbVe could interact with NHL13 gene involved in SA signal pathway via a yeast-two-hybrid screening. In the condition of V. dahliae free, GbVe and NHL13 interacted with each other. However, once stressed by the pathogen, the expression of NHL13 gene decreased whereas the expression level of GbVe displayed significantly increased, indicating that the interactions dissociation between GbVe and NHL13. The enhanced GbVe expression further activated defensive genes expression in SA signal pathway as well as regulating H2O2 and lignin content, which improved the Verticillium wilt resistance of cotton. When silenced GbVe gene in cotton, the plants showed more susceptible. Whereas, the plants displayed no obvious disease resistance difference between NHL13-silent and non-silent seedlings. These funding provides insight into molecular mechanism by which plants integrate SA signal regulated by GbVe to protect themselves from V. dahliae infection.