Involvement of the Mitochondrial Protein Tyrosine Phosphatase PTPM1 in the Promotion of Conidiation, Development, and Pathogenicity in Colletotrichum graminicola.

Shaowei Wang,Guihua Li,Yuejia Dang,Gang Wang,Yi Wei,Shi-Hong Zhang,Penghui Zhang

doi:10.3389/fmicb.2020.605738

Shaowei Wang, Guihua Li + Show 5 more

Open Access

https://doi.org/10.3389/fmicb.2020.605738

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Abstract

The phosphorylation status of proteins, which is determined by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs), governs many cellular actions. In fungal pathogens, phosphorylation-mediated signal transduction has been considered to be one of the most important mechanisms in pathogenicity. Colletotrichum graminicola is an economically important corn pathogen. However, whether phosphorylation is involved in its pathogenicity is unknown. A mitochondrial protein tyrosine phosphatase gene, designated CgPTPM1, was deduced in C. graminicola through the use of bioinformatics and confirmed by enzyme activity assays and observation of its subcellular localization. We then created a CgPTPM1 deletion mutant (ΔCgPTPM1) to analyze its biological function. The results indicated that the loss of CgPTPM1 dramatically affected the formation of conidia and the development and differentiation into appressoria. However, the colony growth and conidial morphology of the ΔCgPTPM1 strains were unaffected. Importantly, the ΔCgPTPM1 mutant strains exhibited an obvious reduction of virulence, and the delayed infected hyphae failed to expand in the host cells. In comparison with the wild-type, ΔCgPTPM1 accumulated a larger amount of H2O2 and was sensitive to exogenous H2O2. Interestingly, the host cells infected by the mutant also exhibited an increased accumulation of H2O2 around the infection sites. Since the expression of the CgHYR1, CgGST1, CgGLR1, CgGSH1 and CgPAP1 genes was upregulated with the H2O2 treatment, our results suggest that the mitochondrial protein tyrosine phosphatase PTPM1 plays an essential role in promoting the pathogenicity of C. graminicola by regulating the excessive in vivo and in vitro production of H2O2.

Highlights

As a whole, phosphorylation and dephosphorylation regulate physiological processes, such as gene expression, signal transduction and the cell cycle, in eukaryotic cells (Zolnierowicz and Bollen, 2000; Cohen, 2001; Tonks, 2013)
Structural biological studies have shown that protein phosphatase (PP) can be divided into three branches based on the different HC(X)5R sequences during the evolution process, and the active motif of protein tyrosine phosphatase (PTP) is HCXXGXXR (Denu and Dixon, 1995, 1998)
The analysis indicated that the N-terminal 124-196 sequences of CgPTPM1 were an active region of PTPs, which contained the conserved catalytic motif HCKAGKGR at positions 142-149, and the essential Cys residue was located at position 143 (Figure 1A)

Summary

Introduction

Phosphorylation and dephosphorylation regulate physiological processes, such as gene expression, signal transduction and the cell cycle, in eukaryotic cells (Zolnierowicz and Bollen, 2000; Cohen, 2001; Tonks, 2013). Protein kinases can phosphorylate serine (Ser), threonine (Thr) or tyrosine (Tyr) residues to form active phosphorylated proteins, and alternatively, PPs can remove the phosphate group from the phosphorylated protein (Guan et al, 1990; Hunter, 1995). Typical PTPs and DUSPs (dual-specificity phosphatases) have similar catalytic mechanisms in the hydrolysis of phosphorylated substrates (Denu and Dixon, 1995, 1998). They share a highly conserved catalytic domain, which has a signature motif HCXXGXXR that forms the catalytic active pocket known as the P-loop (Tu et al, 2020). Studies have shown that when Cys is replaced with Ser, the enzyme will lose its hydrolytic activity in vitro (Ishibashi et al, 1992; Sun et al, 1993), and its function in vivo will be inhibited (Sun et al, 1993; Doi et al, 1994; Aroca et al, 1995)

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