RNA seq of Wild Type, PSR1-expressing plants and PINP1-silenced plants

Phytophthora effector PSR1 suppresses small RNA (sRNA)-mediated immunity in plants, but the underlying mechanism remains unknown. Here, we show that Phytophthora suppressor of RNA silencing 1 (PSR1) contributes to the pathogenicity of Phytophthora sojae and specifically binds to three conserved C-terminal domains of the eukaryotic PSR1-Interacting Protein 1 (PINP1). PINP1 encodes a core pre-mRNA splicing factor PRP16, which unwinds RNA duplexes and binds to pri-miRNAs and general RNAs. Intriguingly, PSR1 decreased both RNA helicase and RNA-binding activity of PINP1, thereby dampening sRNA biogenesis and RNA metabolism. The PSR1-PINP1 interaction caused global changes in alternative splicing (AS). A total of 5,135 genes simultaneously exhibited mis-splicing in both PSR1-overexpressing and PINP1-silenced plants. AS upregulated many mRNA transcripts with their introns retained. The high occurrence of intron-retention (IR) in AS-induced transcripts significantly promoted Phytophthora pathogen infection in Nicotiana benthamiana, which might be caused by the production of truncated proteins. Taken together, our findings uncover a novel role for PINP1 in regulating sRNA biogenesis and plant immunity. mRNA profiles of 6-week-old Wild Type, PSR1-expressing plants and PINP1-silenced plants