Function of Acid Insoluble Lignin and GhLaccase in Cotton Resistance to Verticillium wilt

Abstract

To search cotton resistance to Verticillium wilt, we inoculated Verticillium dahliae into roots of three cotton varieties with different resistance, Pima 90-53, Jimian 20, and Han 208, observed the structure of cell wall, determined the content of lignin and analyzed the transcript level of Laccase. The results showed that, at one day after infection(dpi), the pathogen was unobserved in root vascular tissue of Pima 90-53, while observed in Jimian 20 and Han 208. At 35 days after infection, the cell wall was highly lignified and the vascular was unblocked in Pima 90-53, while there were moderately lignified and slightly blocked in Jimian 20, and lowly lignified and seriously blocked in Han 208. The contents of acid soluble lignin(ASL) and acid insoluble lignin(AIL) in leaves and petioles of the three cotton varieties planted in the diseased nursery were measured. The results showed that the content of AIL was negatively correlated with the disease index of the three cultivars(r = 0.99991*), and the cotent ratio of AIL to ASL was in accord with the verticillium wilt resistance of cotton. The transcript level of Laccase was detected using real-time PCR method, the transcription level of GhLaccase in Jimian 20 was significantly higher than that in Han 208 at any point of test time. The expression level reached the highest at 8 h after infection and maintained the high level within three days. So GhLaccase performed high efficiency in response to the infection of Verticillium dahliae. In conclusion, AIL is positively correlated with the verticillium wilt resistance of cotton, and Laccase plays an important role in cotton resistance to Verticillium dahliae.