A conserved enzyme of smut fungi facilitates cell-to-cell extension in the plant bundle sheath

Abstract

Smut fungi comprise one of the largest groups of fungal plant pathogens causing disease in all cereal crops. They directly penetrate host tissues and establish a biotrophic interaction. To do so, smut fungi secrete a wide range of effector proteins, which suppress plant immunity and modulate cellular functions as well as development of the host, thereby determining the pathogen’s lifestyle and virulence potential. The conserved effector Erc1 (enzyme required for cell-to-cell extension) contributes to virulence of the corn smut Ustilago maydis in maize leaves but not on the tassel. Erc1 binds to host cell wall components and displays 1,3-β-glucanase activity, which is required to attenuate β-glucan-induced defense responses. Here we show that Erc1 has a cell type-specific virulence function, being necessary for fungal cell-to-cell extension in the plant bundle sheath and this function is fully conserved in the Erc1 orthologue of the barley pathogen Ustilago hordei.

Systematic characterization ofUstilago maydissirtuins shows Sir2 as a modulator of pathogenic gene expression

“…We obtained 11 downregulated and 31 upregulated genes (Figure 2D and Supplementary Table S5). Many of the upregulated genes, 58%, encoded for predicted effector proteins, including many of the previously characterized ones: Mig2-6 (Farfsing et al, 2005), Pit1 and 2 (Doehlemann et al, 2011; Mueller et al, 2013), Eff1-7 (Khrunyk et al, 2010), Cmu1 (Djamei et al, 2011), Rsp3 (Ma et al, 2018), Erc1 (Ökmen et al, 2022) and Egl1 and 3 (Schauwecker et al, 1995; Doehlemann et al, 2008). In order to know if the ∆sir2 upregulated genes are genes which have to be expressed when filamentation is induced in PD-charcoal plates, we studied the distribution of the significantly different log2 fold changes in expression of all these genes during charcoal growth, in comparison with axenic conditions, in a wild-type strain (Supplementary Table S6).…”

Systematic characterization of Ustilago maydis sirtuins shows Sir2 as a modulator of pathogenic gene expression

“…We obtained 11 downregulated and 31 upregulated genes ( Figure 2D ; Supplementary Table S5 ). Many of the upregulated genes, 58%, encoded for predicted effector proteins, including many of the previously characterized ones: Mig2-6 ( Farfsing et al, 2005 ), Pit1 and 2 ( Doehlemann et al, 2011 ; Mueller et al, 2013 ), Eff1-7 ( Khrunyk et al, 2010 ), Cmu1 ( Djamei et al, 2011 ), Rsp3 ( Ma et al, 2018 ), Erc1 ( Ökmen et al, 2022 ) and Egl1 and 3 ( Schauwecker et al, 1995 ; Doehlemann et al, 2008 ). In order to know if the ∆sir2 upregulated genes are genes which have to be expressed when filamentation is induced in PD-charcoal plates, we studied the distribution of the significantly different log2 fold changes in expression of all these genes during charcoal growth, in comparison with axenic conditions, in a wild-type strain ( Supplementary Table S6 ).…”

Progress in pathogenesis research of Ustilago maydis, and the metabolites involved along with their biosynthesis

“…For example, U. maydis secretes the effector Cce1 to attenuate callose deposition in the cell wall (Matei & Doehlemann, 2016 ), and the metalloprotease Fly1 can destroy chitinases in host plants (Ökmen et al, 2018 ). The conserved effector protein Erc1 binds to host cell wall components and exhibits 1,3‐β‐glucanase activity, which attenuates the β‐glucan necessary for the induced defence response (Ökmen et al, 2022 ).…”