Pp07886, a glycoside hydrolase family 5 protein from Pythium porphyrae, is a required virulence factor and induces host disease resistance

Abstract

Pythium porphyrae is an important waterborne oomycete pathogen causing red rot disease in the red alga Pyropia yezoensis. However, the virulence factors and pathogenic mechanisms of Pyt. porphyrae remain unknown, hindering the development of prevention and control methods against red rot disease. In this study, the Phytophthora sojae transformation system was used to investigate the virulence factors – glycoside hydrolase family 5 (GH5) in Pyt. porphyrae. The expression of 14 GH5 genes in Pyt. porphyrae at different developmental and infection stages was analyzed. The GH5 gene Pp07886 was significantly induced at the early (30 min post-infection) and middle (5 days post-infection) stages of infection, indicating its critical role in Pyt. porphyrae invasion. Heterologous expression transformant of Phy. sojae (Ps-hePp07886-11) and mutants of Ps4041 (the homolog of Pp07886 in Phy. sojae), PsΔ4041-RFP and PsΔ4041-Pp07886, were generated to evaluated the function of Pp07886. Compared to the wild-type strain, the virulence of Ps-hePp07886-11 increased significantly in soybeans. Compared to PsΔ4041-RFP, the mycelial growth and virulence of PsΔ4041-Pp07886 enhanced. These results indicated that Pp07886 may contribute to growth and virulence. The qRT-PCR and immunoblotting revealed rapid induction of Pp07886 within 3 h post-infection in both Ps-hePp07886-11 and PsΔ4041-Pp07886. Furthermore, the recombinant Pp07886 protein could improve the resistance of soybean to Phy. sojae P6497 infection. These results suggested that Pp07886 may play an important role in oomycete virulence and growth, and could enhance the host resistance to pathogen infection.