Functional Analysis Of GbPAF1 In Cotton Responsive To Verticillium Dahliae

The ubiquitin/26 S proteasome plays significant roles in plant development and immunity. In our previous study, a protein was screened by proteomic analysis and found induced sharply in cotton by Verticillium dahliae infection(Gao et al 2013). This protein shows high similarity to the sixth subunit of α subunit for ubiquitin-proteasome in Arabidopsis and named Gb PAF1. Gb PAF1 was obtained and its functions in cotton development and response to V. dahliae were investigated. The main results were as follows:1. There is no obvious difference in expression pattern of Gb PAF1 among tissues with high expression level. The expression vector of GFP fused with the N terminal of Gb PAF1 was completed and transiently expressed in tobacco. The result showed that Gb PAF1 was located in cell membrane and nucleus.2. The expression level of Gb PAF1 was down regulated by virus induced gene silencing, and the cotton plants showed noticeable dwarf, curly and smaller leaves. Meanwhile, more axillary buds and smaller cells in stem were found compared with the control. In addition, the content of auxin declined apparently when Gb PAF1 was silenced. This suggests that Gb PAF1 may be involved in cotton development regulation through auxin hemeostasis or signal pathway, but the mechanism is still unclear.3. Compared with the mock, cotton plants with silenced Gb PAF1 became more susceptible to strain V991 of V. dahliae. In addition, Gene expression pattern analysis showed that JA and SA pathway were inhibited partially. However, no significant difference was found between TRV::Gb PAF1 and TRV::00 when they inoculated with necrotrophic fungus Botrytis cinerea.4. Over-expression and down-regulated expression of Gb PAF1 transgenetic cotton plants were obtained. And the expression level of genes involved SA signaling pathway, like PR2 and PR5, decreased significantly in over-expression transgenetic plants, while opposite results were obtained for genes involeved in JA signal pathway, like Lox1 and Lox2. Nevertheless, Both JA and SA signal pathways were activated in Gb PAF1 silenced plants through RNA interference.All the results suggested that PAF1 involved in cotton development through regulating the synthesis of auxin. And PAF1 could regulate cotton immunity responseby coordinating the signaling pathwway of JA and SA upon infection with V. dahliae. The exact mechanisms remain to be resolved.