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; Dongmei Li; Yang Bi; Dov B Prusky; Yupeng Dong; Tiaolan Wang; Miao Zhang; Xuemei Zhang; Yongxiang Liu

doi:10.3389/fmicb.2020.01279

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

Front Microbiol. 2020 Jun 30:11:1279. doi: 10.3389/fmicb.2020.01279. eCollection 2020.

Authors

Yi Huang¹, Yongcai Li², Dongmei Li¹, Yang Bi¹, Dov B Prusky^{1

2}, Yupeng Dong¹, Tiaolan Wang¹, Miao Zhang¹, Xuemei Zhang¹, Yongxiang Liu¹

Affiliations

¹ College of Food Science and Engineering, Gansu Agricultural University, Lanzhou, China.
² Institute of Postharvest and Food Sciences, The Volcani Center, Agricultural Research Organization, Rishon LeZion, Israel.

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.

Keywords: Alternaria alternata; calcium signal pathway; hydrophobicity; pear fruit wax; phospholipase C.