The secreted repetitive protein Rsp3 of Ustilago maydis is required for full virulence
Ma, L. S.; Trippel, C.; Wang, L.; Mendoza - Mendoza, Artemio; Ullmann, S.; Moretti, M.; Wawra, S.; Reissmann, S.; Munch, K.; Kahmann, R.
The biotrophic fungus Ustilago maydis causes smut disease in maize. Hallmarks of the disease are the formation of tumor and anthocyanin induction. Here, we show that the repetitive secreted protein Rsp3 is required for virulence and anthocyanin accumulation. Rsp3 consists of several repetitive as well as a Cys-rich domain and is highly expressed during the biotrophic stage. Interestingly, rsp3 alleles obtained from field isolates of U. maydis differ in size ranging from 1.8 to 2.5kb. These size differences are caused by reduced or expanded numbers of certain repeats. The shortest rsp3 allele from a strain collected in Toluca valley in Mexico into the U. maydis rsp3 mutant, could fully restore virulence, illustrating full functionality. Rsp3 can be easily be detected in culture supernatants when expressed from a constitutive promoter. The protein showed highly anomalous migration behavior on SDS-PAGE that did not depend on the presence of the Cys-rich domain. Furthermore, deletion of the Cys-rich domain of Rsp3 prevented tumor induction but anthocyanin induction was still observed. This suggests that Rsp3 could be a dual function effector.... [Show full abstract]
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