AUTHOR=Zhang Miao , Li Yongcai , Wang Tiaolan , Bi Yang , Li Rong , Huang Yi , Mao Renyan , Jiang Qianqian , Liu Yongxiang , Prusky Dov B. 

TITLE=AaPKAc Regulates Differentiation of Infection Structures Induced by Physicochemical Signals From Pear Fruit Cuticular Wax, Secondary Metabolism, and Pathogenicity of Alternaria alternata

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.642601

DOI=10.3389/fpls.2021.642601

ISSN=1664-462X

ABSTRACT=<p><italic>Alternaria alternata</italic>, the casual agent of black rot of pear fruit, can sense and respond to the physicochemical cues from the host surface and form infection structures during infection. To evaluate the role of cyclic AMP-dependent protein kinase (cAMP-PKA) signaling in surface sensing of <italic>A. alternata</italic>, we isolated and functionally characterized the cyclic adenosine monophosphate-dependent protein kinase A catalytic subunit gene (<italic>AaPKAc</italic>). Gene expression results showed that <italic>AaPKAc</italic> was strongly expressed during the early stages of appressorium formation on hydrophobic surfaces. Knockout mutants Δ<italic>AaPKAc</italic> were generated by replacing the target genes via homologous recombination events. We found that intracellular cAMP content increased but PKA content decreased in Δ<italic>AaPKAc</italic> mutant strain. Appressorium formation and infection hyphae were reduced in the Δ<italic>AaPKAc</italic> mutant strain, and the ability of the Δ<italic>AaPKAc</italic> mutant strain to recognize and respond to high hydrophobicity surfaces and different surface waxes was lower than in the wild type (WT) strain. In comparison with the WT strain, the appressorium formation rate of the Δ<italic>AaPKAc</italic> mutant strain on high hydrophobicity and fruit wax extract surface was reduced by 31.6 and 49.3% 4 h after incubation, respectively. In addition, <italic>AaPKAc</italic> is required for the hypha growth, biomass, pathogenicity, and toxin production of <italic>A. alternata</italic>. However, <italic>AaPKAc</italic> negatively regulated conidia formation, melanin production, and osmotic stress resistance. Collectively, <italic>AaPKAc</italic> is required for pre-penetration, developmental, physiological, and pathological processes in <italic>A. alternata.</italic></p>