Critical role of AaTgl1 lipase/hydrolase in virulence and lesion formation in Alternaria alternata.

Authors

Jessalyn Marasigan Parco, Celine Yen Ling Choo, Hsin-Yu Lu, Pei-Ching Wu, Kuang-Ren Chung

Published in

Fungal biology. Volume 130. Issue 7. Pages 101835. Epub Aug 10, 2026.

Abstract

Lipases and hydrolases play important roles in diverse biological processes in fungi. Their roles in virulence in the phytopathogenic fungus Alternaria alternata remain poorly understood. The AaTgl1 protein of A. alternata is a putative lipase/hydrolase characterized by a triacylglycerol lipase domain, an α/β-hydrolase superfamily domain, and a catalytic triad (Ser353, Asp522, His548) within the conserved GxSxG motif. Sequence analysis revealed only 64-68% similarity to orthologs from other filamentous fungi, suggesting a specialized role in lipid metabolism that may contribute to the ecological success of Alternaria. Targeted deletion of AaTgl1 (ΔAaTgl1) demonstrated its essential role in fungal development: mutants exhibited reduced vegetative growth, impaired conidiation, defective germination, and diminished formation of appressorium-like structures. Genetic complementation restored wild-type phenotypes, confirming the specific requirement for AaTgl1. Lipid droplet staining showed that AaTgl1 is indispensable for lipid storage and mobilization. ΔAaTgl1 accumulated elevated levels of reactive oxygen species, exhibited heightened sensitivity to oxidative stress, and displayed increased cell wall damage, implicating AaTgl1 in redox homeostasis and structural integrity. Although dispensable for toxin biosynthesis, ΔAaTgl1 showed markedly attenuated virulence on calamondin leaves, suggesting a role in overcoming host defenses. Collectively, these findings indicate that AaTgl1 is a multifunctional lipase/hydrolase that integrates lipid metabolism, stress tolerance, and morphogenesis, thereby serving as a critical determinant of fungal fitness and pathogenicity in A. alternata. This study provides new insights into the molecular mechanisms linking lipid regulation to fungal development, host adaptation, and virulence.

PMID:
42875110
Bibliographic data and abstract were imported from PubMed on 15 Oct 2026.

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