Phospholipase C From Alternaria alternata Is Induced by Physiochemical Cues on the Pear Fruit Surface That Dictate Infection Structure Differentiation and Pathogenicity.

Yi Huang,Yongcai Li,Dov B Prusky,Tiaolan Wang,Yongxiang Liu,Dongmei Li,Xuemei Zhang,Yang Bi,Miao Zhang,Yupeng Dong

doi:10.3389/fmicb.2020.01279

Yi Huang, Yongcai Li + Show 8 more

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https://doi.org/10.3389/fmicb.2020.01279

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Abstract

To investigate the mechanisms of phospholipase C (PLC)-mediated calcium (Ca2+) signaling in Alternaria alternata, the regulatory roles of PLC were elucidated using neomycin, a specific inhibitor of PLC activity. Three isotypes of PLC designated AaPLC1, AaPLC2, and AaPLC3 were identified in A. alternata through genome sequencing. qRT-PCR analysis showed that fruit wax extracts significantly upregulated the expression of all three PLC genes in vitro. Pharmacological experiments showed that neomycin treatment led to a dose-dependent reduction in spore germination and appressorium formation in A. alternata. Appressorium formation was stimulated on hydrophobic and pear wax-coated surfaces but was significantly inhibited by neomycin treatment. The appressorium formation rates of neomycin treated A. alternata on hydrophobic and wax-coated surfaces decreased by 86.6 and 47.4%, respectively. After 4 h of treatment, exogenous CaCl2 could partially reverse the effects of neomycin treatment. Neomycin also affected mycotoxin production in alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT), and tentoxin (TEN), with exogenous Ca2+ partially reversing these effects. These results suggest that PLC is required for the growth, infection structure differentiation, and secondary metabolism of A. alternata in response to physiochemical signals on the pear fruit surface.

Highlights

Alternaria alternata is a phytopathogen that infects an array of plants, leading to the spoilage of fruits and vegetables post-harvest and during transport
Several Alternaria species can produce toxic secondary metabolites including alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT), and tentoxin (TEN; Ostry, 2008), some of which are phytotoxins that mediate fungal pathogenicity, Alternaria alternata AaPLC Regulates Infection with others defined as mycotoxins that elicit adverse effects in humans and animals (EFSA, 2011; Meena et al, 2017)
phospholipase C (PLC) plays an important role in vegetative growth, conidia, Ca2+ homeostasis, and the pathogenicity of citrus A. alternata (Tsai and Chung, 2014). These results suggest that PLC regulates the morphogenesis of pathogenic fungi

Summary

Introduction

Alternaria alternata is a phytopathogen that infects an array of plants, leading to the spoilage of fruits and vegetables post-harvest and during transport. Several Alternaria species can produce toxic secondary metabolites including alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT), and tentoxin (TEN; Ostry, 2008), some of which are phytotoxins that mediate fungal pathogenicity, Alternaria alternata AaPLC Regulates Infection with others defined as mycotoxins that elicit adverse effects in humans and animals (EFSA, 2011; Meena et al, 2017). One of the most potent counter-strategies is the development of target site-specific chemicals that inhibit fungal infections. Exploring the molecular aspects of pathogenfruit interactions has biological and economic significance as a means to develop rational alternatives for disease control

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