Cyclophilin BcCyp2 Regulates Infection-Related Development to Facilitate Virulence of the Gray Mold Fungus Botrytis cinerea.

Jiao Sun,Song Yang,Qing-Ming Qin,Hao-Wu Chang,Ming-Zhe Zhang,Chen-Hao Sun,Gui-Hua Li,Yue Liu,Jie Hou,Hao Zhang

doi:10.3390/ijms22041694

Abstract

Cyclophilin (Cyp) and Ca2+/calcineurin proteins are cellular components related to fungal morphogenesis and virulence; however, their roles in mediating the pathogenesis of Botrytis cinerea, the causative agent of gray mold on over 1000 plant species, remain largely unexplored. Here, we show that disruption of cyclophilin gene BcCYP2 did not impair the pathogen mycelial growth, osmotic and oxidative stress adaptation as well as cell wall integrity, but delayed conidial germination and germling development, altered conidial and sclerotial morphology, reduced infection cushion (IC) formation, sclerotial production and virulence. Exogenous cyclic adenosine monophosphate (cAMP) rescued the deficiency of IC formation of the ∆Bccyp2 mutants, and exogenous cyclosporine A (CsA), an inhibitor targeting cyclophilins, altered hyphal morphology and prevented host-cell penetration in the BcCYP2 harboring strains. Moreover, calcineurin-dependent (CND) genes are differentially expressed in strains losing BcCYP2 in the presence of CsA, suggesting that BcCyp2 functions in the upstream of cAMP- and Ca2+/calcineurin-dependent signaling pathways. Interestingly, during IC formation, expression of BcCYP2 is downregulated in a mutant losing BcJAR1, a gene encoding histone 3 lysine 4 (H3K4) demethylase that regulates fungal development and pathogenesis, in B. cinerea, implying that BcCyp2 functions under the control of BcJar1. Collectively, our findings provide new insights into cyclophilins mediating the pathogenesis of B. cinerea and potential targets for drug intervention for fungal diseases.

Highlights

Botrytis cinerea is a typical necrotrophic fungal pathogen that causes gray mold on over 1000 plant species, including almost all vegetable and fruit crops [1], and annually causes economic losses of USD 10 to 100 billion worldwide [2]
To identify virulence-associated factors that mediate pathogenesis of B. cinerea, and to understand molecular mechanisms underlying the interactions between B. cinerea and its hosts, we screened pathogenicity-attenuated mutants from a B. cinerea library that contains
~50,000 transformants generated by Agrobacterium tumefaciens-mediated transformation (ATMT) approach [31,32,33] and identified pathogenicity-reduced mutant strain M331

Summary

Introduction

Botrytis cinerea is a typical necrotrophic fungal pathogen that causes gray mold on over 1000 plant species, including almost all vegetable and fruit crops [1], and annually causes economic losses of USD 10 to 100 billion worldwide [2]. The main infection source of the pathogen is conidia that attach on the surface of plants, germinate and form appressoria or appressorium-like infection structures to facilitate host penetration [4]. During interactions with its hosts, the pathogen employs diverse virulence-associated factors, including cell wall degrading enzymes, cutinases, toxins, hormones, small RNAs and other pathogenesisrelated factors, to facilitate host infection. These factors function coordinately to enable the pathogen to induce the silencing of host immune response genes, kill host cells, break down the dead host tissues and assimilate nutrients from the killed host cells to support its growth [2,8,9]. When the environment is suitable, the sclerotia germinate, form mycelia and conidiophores, and produce a large number of conidia; with the aids of wind, rain, irrigation water and farming tools, conidia land on plant surfaces and start a new round of infection [3]

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Results

Conclusion