Work

The secreted GH43 protein VpGHa1 functions as an effector to suppress plant immunity and contributes to stress adaptation in Valsa pyri

Year: 2026

Type: article

Abstract: Introduction While the pear canker pathogen Valsa pyri typically employs cell wall-degrading enzymes to breach host barriers, the functions of its glycoside hydrolase family 43 (GH43) proteins remain largely unexplored. Methods Here, using genetic manipulation, secretion assays, transient-expression assays, and transcriptomic analysis, we investigated whether the GH43 protein VpGHa1 contributes to fungal virulence, stress adaptation, and suppression of host immunity. Results VpGHa1 contains a predicted signal peptide and a GH43_AnAbnA-like domain. VpGHa1 expression was strongly induced during the early stages of infection, and the protein was confirmed to be secreted. Sequence analysis predicted an endo-1,5-α-L-arabinofuranosidase-related function, and recombinant VpGHa1 showed positive anti-arabinase immunoreactivity in an antibody-based ELISA. Deletion of VpGHa1 reduced lesion size on pear twigs by 33.8%, whereas genetic complementation significantly restored the reduced-virulence phenotype and overexpression enhanced pathogenicity without affecting vegetative growth. The ΔVpGHa1 mutant showed increased tolerance to KCl but greater sensitivity to NaCl and H₂O₂, indicating that VpGHa1 contributes to ionic and oxidative stress adaptation. Furthermore, transient expression of VpGHa1 in Nicotiana benthamiana suppressed BAX- and INF1-induced cell death, promoted colonization by Sclerotinia sclerotiorum, and enhanced lesion formation after V. pyri challenge in apple leaves; this was accompanied by downregulation of apple defense-related genes. Transcriptomic analysis identified 115 DEGs between the WT and ΔVpGHa1 mutant and revealed enrichment of carbohydrate-related, extracellular/cell-surface-associated, and metabolic processes, suggesting broad transcriptional effects associated with cell-surface and metabolic adaptation. Discussion Together, these findings identify VpGHa1 as a multifunctional secreted GH43 virulence factor linking pathogenicity, stress adaptation, and host immune suppression, whereas its predicted arabinan-related enzymatic activity remains to be experimentally validated.

Source: Frontiers in Plant Science

DOI: 10.3389/fpls.2026.1979662