Glutathione peroxidase LtGPX3 contributes to oxidative stress tolerance, virulence, and plant defense suppression in the peach gummosis fungus Lasiodiplodia theobromae

Abstract

The notorious woody plant-degrading pathogen Lasiodiplodia theobromae is a major causal agent of peach gummosis, one of the prevalent and devastating trunk diseases to peach production; however, its pathogenesis is largely unknown. Our previous study showed that L. theobromae LtGPX3, which encodes a glutathione peroxidase resembling yeast GPX3/HYR1-like, was constantly and dramatically upregulated at the infectious stages. Here, we functionally characterized LtGPX3 using the CRISPR-Cas9-aided split marker approach. The ΔLtgpx3 deletion mutants displayed increased sensitivity to the osmotic stress agent KCl and less sensitivity to the cell wall-damaging agent calcofluor white. Exogenous oxidants highly induced the expression of LtGPX3, and the ΔLtgpx3 mutants displayed increased sensitivity to ROS-generating oxidants. Pathogenicity assays revealed that ΔLtgpx3 mutants showed compromised virulence in peach shoots, which was partially restored when peach shoots were pretreated with an NADPH oxidase inhibitor before inoculation. Moreover, ROS levels were strongly boosted, and transcripts of plant defense-related genes were highly induced in the ΔLtgpx3 mutants-infected peach shoots compared with the wild-type-inoculated. Overall, our results showed the essential roles of LtGPX3 in the oxidative stress response and tolerance and pathological functions in L. theobromae. These findings deepen our understanding of the survival strategies of the woody plant-degrading pathogen L. theobromae and provide new insights into developing new strategies for peach gummosis disease control.