The Mitogen-Activated Protein Kinase Kinase VdPbs2 of Verticillium dahliae Regulates Microsclerotia Formation, Stress Response, and Plant Infection

Abstract

Verticillium dahliae, a ubiquitous phytopathogenic fungus, forms resting structures, known as microsclerotia that play crucial roles in Verticillium wilt diseases. VdHog1, a mitogen-activated protein kinase (MAPK), controls microsclerotia formation, virulence, and stress response in V. dahliae. In this study, we present detailed evidence that the conserved upstream component of VdHog1, VdPbs2, is a key regulator of microsclerotia formation, oxidative stress and fungicide response and plant virulence in V. dahliae. We identified VdPbs2, homologous to the yeast MAPK kinase Pbs2. Similar to the VdHog1 deletion mutant, VdPbs2 deletion strains exhibited delayed melanin synthesis and reduced formation of microsclerotia. When exposed to stresses, VdPbs2 mutants were more sensitive than the wild type to osmotic agents and peroxide, but more resistant to inhibitors of cell wall synthesis and some fungicides. Finally, VdPbs2 deletion mutants exhibited reduced virulence on smoke tree and tobacco seedlings. When taken together, we implicate that VdPbs2 and VdHog1 function in a cascade that regulates microsclerotia formation and virulence, but not all VdHog1 dependent functions are VdPbs2 regulated. This study thus provides novel insights into the signal transduction mechanisms that regulate microsclerotia formation and pathogenesis in this fungus.

The Verticillium dahliae Sho1‐MAPK pathway regulates melanin biosynthesis and is required for cotton infection

“…dahliae (Figs B, , and , Fig. S8), and the role of the MAPK pathways in melanin biosynthesis is well characterized (Tzima et al ., ; Tian et al ., ; Tian et al ., ; Wang et al ., ; Yu et al ., ; Zheng et al ., ). Although VdSho1 did not show significant growth changes in response to nystatin, melanin accumulation, however, affected the membrane permeability mediated by nystatin treatment (Fig.…”

“…Undoubtedly, gene deletion studies of various MAPK cascade components suggest a strong correlation between melanin biosynthesis and virulence in V . dahliae (Tzima et al ., ; Tian et al ., ; Tian et al ., ; Wang et al ., ; Yu et al ., ; Zheng et al ., ). Thus, the degree of influence of melanin may be contingent on the strain, and the host type challenged.…”

“…Similarly, in V . dahliae melanin biosynthesis driven by sensor and MAPK cascades is correlated with pathogenicity in some studies (Tzima et al ., ; Tian et al ., ; Tian et al ., ; Wang et al ., ; Yu et al ., ; Zheng et al ., ). Deletion of the V .…”

“…For instance, deletion of the V. dahliae surface sensor gene Msb2 (VdMsb) significantly decreased virulence on cotton (Tian et al, 2014). Verticillium dahliae sensors and MAPK cascades also participate in signal transduction processes leading to melanin biosynthesis (Tzima et al, 2010;Tian et al, 2014;Tian et al, 2016;Wang et al, 2016;Wang et al, 2018;Yu et al, 2019;Zheng et al, 2019).…”

Verticillium wilt caused by Verticillium dahliae in woody plants with emphasis on olive and shade trees

“…It was also confirmed that VDH1, encoding a class II hydrophobin, is involved in the formation of microsclerotia (Klimes et al 2008;Klimes and Dobinson 2006). In addition, many genes have been characterized that are involved in signal transduction pathways and regulation of microsclerotia formation of V. dahliae, such as VMK1, encoding a mitogen-activated protein kinase (Rauyaree et al 2005), VdGARP1, encoding a glutamic acid-rich protein , the G protein β subunit (named as VGB) (Tzima et al 2012), Vta2, encoding a nuclear zinc finger protein, (Tran et al 2014), the MADS-box transcription factor VdMcm1 , the mitogen-activated protein kinase (MAPK) Hog1 , and the MAPK Msb and Pbs2 Tian et al 2016). Unravelling the functional characterizations of these genes provides insight into the genetic control of microsclerotia formation in V. dahliae.…”