The APSES transcription factor Vst1 is a key regulator of development in microsclerotium‐ and resting mycelium‐producing Verticillium species

Abstract

SUMMARYPlant pathogens of the genus Verticillium pose a threat to many important crops worldwide. They are soil-borne fungi which invade the plant systemically, causing wilt symptoms. We functionally characterized the APSES family transcription factor Vst1 in two Verticillium species, V. dahliae and V. nonalfalfae, which produce microsclerotia and melanized hyphae as resistant structures, respectively. We found that, in V. dahliae Dvst1 strains, microsclerotium biogenesis stalled after an initial swelling of hyphal cells and cultures were never pigmented. In V. nonalfalfae Dvst1, melanized hyphae were also absent. These results suggest that Vst1 controls melanin biosynthesis independent of its role in morphogenesis. The absence of vst1 also had a great impact on sporulation in both species, affecting the generation of the characteristic verticillate conidiophore structure and sporulation rates in liquid medium. In contrast with these key roles in development, Vst1 activity was dispensable for virulence. We performed a microarray analysis comparing global transcription patterns of wild-type and Dvst1 in V. dahliae. G-protein/cyclic adenosine monophosphate (G-protein/cAMP) signalling and mitogen-activated protein kinase (MAPK) cascades are known to regulate fungal morphogenesis and virulence. The microarray analysis revealed a negative interaction of Vst1 with G-protein/ cAMP signalling and a positive interaction with MAPK signalling. This analysis also identified Rho signalling as a potential regulator of morphogenesis in V. dahliae, positively interacting with Vst1. Furthermore, it exposed the association of secondary metabolism and development in this species, identifying Vst1 as a potential co-regulator of both processes. Characterization of the putative Vst1 targets identified in this study will aid in the dissection of specific aspects of development.

Verticillium dahliae transcription factor VdFTF1 regulates the expression of multiple secreted virulence factors and is required for full virulence in cotton

“…In V. dahliae , TFs such as VdSge1 also exhibit pleiotropic effects, including the requirement for radial growth, conidial production and pathogenicity (Santhanam and Thomma, ). Vdpf regulates melanized microsclerotia formation, conidial production and pathogenicity (Luo et al ., ), and Vst1 controls melanin biosynthesis, morphogenesis and secondary metabolism (Sarmiento‐Villamil et al ., ). In contrast, the phenotypes of all VdFTF1‐ deletion strains were similar to that of the wild‐type strain during cultivation on PDA medium, and they also exhibited similar conidial morphology and production (Fig.…”

“…As our understanding of the pathogenicity of V. dahliae increases, it appears that a variety of genes are required for virulence towards host plants, including protein kinases (Rauyaree et al ., ; Tian et al ., ; Tzima et al ., ), TFs (Luo et al ., ; Santhanam et al ., ; Sarmiento‐Villamil et al ., ; Tran et al ., ; Xiong et al ., ), effectors (de Jonge et al ., ; Liu et al ., ; Santhanam et al ., ), enzymes involved in plant cell wall degradation (Chen et al ., ; Liu et al ., ; Maruthachalam et al ., ) and other functional genes (Gao et al ., ; Klimes and Dobinson, ; Li et al ., ; Maruthachalam et al ., ; Santhanam et al ., ; Zhang DD et al ., ; Zhang YL et al ., ). In this study, we identified a new pathogenicity and virulence‐related gene encoding a Fungal_trans domain‐containing TF (Figs and ).…”

“…The function of VdFTF1 in pathogenesis appears to be primarily related to the regulation of genes involved in catalytic processes (233 genes), especially proteins that are associated with hydrolase and oxidoreductase activity (Fig. B), which are important for pathogenesis in V. dahliae (Sarmiento‐Villamil et al ., ; Tran et al ., ; Tzima et al ., ). The importance of effectors in interactions between host plants and V. dahliae has been established previously (Santhanam et al ., ; Sarmiento‐Villamil et al ., ; Tran et al ., ).…”

“…B), which are important for pathogenesis in V. dahliae (Sarmiento‐Villamil et al ., ; Tran et al ., ; Tzima et al ., ). The importance of effectors in interactions between host plants and V. dahliae has been established previously (Santhanam et al ., ; Sarmiento‐Villamil et al ., ; Tran et al ., ). In the current study, the expression of potential effector genes was affected in the VdFTF1 gene‐deletion strains, including 14 SCRPs (Fig.…”

“…The reference genome of V. dahliae strain VdLs.17 is predicted to encode 530 TFs classified into 42 TF families (Klosterman et al ., ; Park et al ., ). Like the TFs in other phytopathogens, V. dahliae TFs, including VdSge1 (Santhanam and Thomma, ), Vta2 (Tran et al ., ), VdCrz1 (Xiong et al ., ), Vdpf (Luo et al ., ) and Vst1 (Sarmiento‐Villamil et al ., ), also play important roles in processes involved in pathogenicity, microsclerotium development and morphological development. In addition, gene activity during V. dahliae pathogenesis is regulated by several important signalling factors (Rauyaree et al ., ; Tian et al ., ; Tzima et al ., ) that positively regulate virulence factors.…”