Botrytis cinerea G Protein β Subunit Bcgb1 Controls Growth, Development and Virulence by Regulating cAMP Signaling and MAPK Signaling.

Jiejing Tang,Guoqing Li,Mingde Wu,Jing Zhang,Long Yang

doi:10.3390/jof7060431

Jiejing Tang, Guoqing Li + Show 3 more

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https://doi.org/10.3390/jof7060431

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Abstract

Botrytis cinerea is a necrotrophic phytopathogenic fungus that causes gray mold disease in many crops. To better understand the role of G protein signaling in the development and virulence of this fungus, the G protein β subunit gene Bcgb1 was knocked out in this study. The ΔBcgb1 mutants showed reduced mycelial growth rate, but increased aerial hyphae and mycelial biomass, lack of conidiation, failed to form sclerotia, increased resistance to cell wall and oxidative stresses, delayed formation of infection cushions, and decreased virulence. Deletion of Bcgb1 resulted in a significant reduction in the expression of several genes involved in cAMP signaling, and caused a notable increase in intracellular cAMP levels, suggesting that G protein β subunit Bcgb1 plays an important role in cAMP signaling. Furthermore, phosphorylation levels of MAP kinases (Bmp1 and Bmp3) were increased in the ΔBcgb1 mutants. Yeast two-hybrid assays showed that Bcgb1 interacts with MAPK (Bmp1 and Bmp3) cascade proteins (BcSte11, BcBck1, BcMkk1, and BcSte50), and the Bmp1-regulated gene Bcgas2 was up-regulated in the ΔBcgb1 mutant. These results indicated that Gβ protein Bcgb1 is involved in the MAPK signaling pathway in B. cinerea. In summary, our results revealed that Gβ protein Bcgb1 controls development and virulence through both the cAMP and MAPK (Bmp1 and Bmp3) signaling pathways in B. cinerea.

Highlights

Among the known Gβ protein in the Protein Data Bank (PDB), the crystal structure of Bcgb1 was predicted by using R. norvegicus Gβ protein (PDB: 7cfm.1.B) as a template (Figure 1B)
These results indicate that Bcgb1 plays an important role in hyphal growth, conidiation, and sclerotia formation
Due to the cAMP levels having increased in ΔBcgb1 mutants, we further examined the transcript levels of the cAMP signaling pathway-related genes, such as the adenylate cyclase gene Bac, two phosphodiesterase genes (BcPde1 and BcPde2), and three cAMP-dependent protein kinase (PKA) encoding genes (BcPka1, BcPka2, and BcPkaR)

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Botrytis cinerea is an important phytopathogenic fungus and the causal agent of gray mold disease in more than 1400 plant species. It is responsible for significant economic losses in many important vegetables, fruits, and ornamentals [1]. The cost of controlling gray mold disease in the world has been estimated at over €1 billion per year. Due to its scientific and economic importance, B. cinerea is considered as the second most important fungal pathogen and the necrotrophic model fungus [2]. In the life cycle of B. cinerea, there are four different structures, including conidia, mycelia, sclerotia, and ascospores

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