Functional Analysis Of MYC2-Like Gene In Cotton Responsive To Verticillium Dahliae

Verticillium wilt of cotton (Gossypium hirsutum) is a widespread and destructive disease that is caused by the soil-borne fungus pathogen Verticillium dahliae. Jasmonic acid (JA) and Salicylic acid (SA) are essential signaling molecules that coordinate the plant response to biotic and abiotic challenges, in addition to several developmental processes. The basic-helix-loop-helix (bHLH) transcription factor (TF) MYC2 has recently emerged as a master regulator of most aspects of the jasmonate (JA) signaling pathway in Arabidopsis. MYC2 coordinates JA-mediated defense responses by antagonistically regulating two different branches of the JA signaling pathway that determine resistance to pests and pathogens, respectively. In present study, a MYC2-like gene, GhMYC2-like, was used and transferred into G. hirsutum cv. YZ-1 (susceptible to V. dahliae). The transcriptional level of GhMYC2-like was up regulated in transgenic cotton plants as compared to wild types upon JA treatments. It was also observe that GhMYC2-like up regulates the expression of those genes were involved JA-mediated response defense to pathogens. While GhMYC2-like expression was suppressed after SA treatment GhMYC2-like induced transgenic lines were subjected to insect feeding stress. Results revealed that the effects of insect feeding were very less on leaves of transgenic lines that probably due to the GhMYC2-like induced JA defense system against insects. Constitutively overexpressing of GhMYC2-like transgenic plants displayed a noteworthy tolerance against herbivores, which supports our hypothesis. Overall, these results are consistent with the observation that GhMYC2-like is a positive regulator of a subset of JA-responsive genes involved in pathogen and insects stress. Virus induced gene silencing (VIGS) is post-transcriptional gene silence technique, which offers an alternative and complimentary approach for large-scale functional analysis of individual genes by knocking down the expression of endogenous genes. GbMYC2-like gene was introduced into G. barbedense cv.’7124’(resistant to V. dahliae) via Agrobecterium. Roots and leaves of TRV:GbMYC2-like silenced and TRV:00-control plants were subjected to fungus stress by V. dahliae and B. cinerea. The results signifying that GbMYC2-like induced plants exhibited more sensitivity to V. dahliae as comparison to control-inoculated plants, rate of diseased plants and disease index was also higher in GbMYC2-like induced plants. In addition, lesions caused by fungal disease B. cinerae were also larger on the leaves of GbMYC2-like induced plants. Based on these results, it was clearly understood that silencing of this gene enhanced plant susceptibility to V. dahliae infection. The results obtained from this experiment indicate that MYC2-like is a master regulator within the JA signaling pathway and controls a wide range of responses to the biotic and abiotic environment as well as several developmental programs. These studies enabled us to find out different expression levels of MYC2-like at different environmental stresses in both Gossypium hirsutum and Gossypium barbedense. Thus, it could be assumed that MYC2-like is an essential component for cotton resistance to V. dahliae infection.