The G-protein alpha subunit AaGA1 positively regulates vegetative growth, appressorium-like formation, and pathogenicity in Alternaria alternata.

This article focuses on the characterization and functional analysis of AaGA1, a G protein alpha (Gα) subunit, in the fungal pathogen Alternaria alternata, which causes pear black spot disease. The study demonstrates that deletion of AaGA1 impairs fungal vegetative growth, conidiation, spore germination, appressorium-like formation, and penetration ability, leading to reduced pathogenicity on pear fruits and tobacco leaves. Additionally, AaGA1 deletion decreases melanin and mycotoxin production and downregulates genes related to sporulation and cell wall-degrading enzymes, indicating its role in fungal development, stress response, and virulence. These findings provide a basis for further investigation into the molecular mechanisms of AaGA1 in A. alternata’s infection process and may inform targeted strategies for controlling postharvest disease in pears.