Mining oomycete proteomes for phosphatome leads to the identification of specific expanded phosphatases in oomycetes.

Phosphatases are important regulators of protein phosphorylation and various cellular processes, and they serve as counterparts to kinases. In this study, our comprehensive analysis of oomycete complete proteomes unveiled the presence of approximately 3833 phosphatases, with most species estimated to have between 100 and 300 putative phosphatases. Further investigation of these phosphatases revealed a significant increase in protein serine/threonine phosphatases (PSP) within oomycetes. In particular, we extensively studied the metallo-dependent protein phosphatase (PPM) within the PSP family in the model oomycete Phytophthora sojae. Our results showed notable differences in the expression patterns of PPMs throughout 10 life stages of P. sojae, indicating their vital roles in various stages of oomycete pathogens. Moreover, we identified 29 PPMs in P. sojae, and eight of them possessed accessory domains in addition to phosphate domains. We investigated the biological function of one PPM protein with an extra PH domain (PPM1); this protein exhibited high expression levels in both asexual developmental and infectious stages. Our analysis confirmed that PPM1 is indeed an active protein phosphatase, and its accessory domain does not affect its phosphatase activity. To delve further into its function, we generated knockout mutants of PPM1 and validated its essential roles in mycelial growth, sporangia and oospore production, as well as infectious stages. To the best of our knowledge, this study provides the first comprehensive inventory of phosphatases in oomycetes and identifies an important phosphatase within the expanded serine/threonine phosphatase group in oomycetes.

The Phytophthora sojae nuclear effector PsAvh110 targets a host transcriptional complex to modulate plant immunity.

Plants have evolved sophisticated immune networks to restrict pathogen colonization. In response, pathogens deploy numerous virulent effectors to circumvent plant immune responses. However, the molecular mechanisms by which pathogen-derived effectors suppress plant defenses remain elusive. Here, we report that the nucleus-localized RxLR effector PsAvh110 from the pathogen Phytophthora sojae, causing soybean (Glycine max) stem and root rot, modulates the activity of a transcriptional complex to suppress plant immunity. Soybean like-heterochromatin protein 1-2 (GmLHP1-2) and plant homeodomain finger protein 6 (GmPHD6) form a transcriptional complex with transcriptional activity that positively regulates plant immunity against Phytophthora infection. To suppress plant immunity, the nuclear effector PsAvh110 disrupts the assembly of the GmLHP1-2/GmPHD6 complex via specifically binding to GmLHP1-2, thus blocking its transcriptional activity. We further show that PsAvh110 represses the expression of a subset of immune-associated genes, including BRI1-associated receptor kinase 1-3 (GmBAK1-3) and pathogenesis-related protein 1 (GmPR1), via G-rich elements in gene promoters. Importantly, PsAvh110 is a conserved effector in different Phytophthora species, suggesting that the PsAvh110 regulatory mechanism might be widely utilized in the genus to manipulate plant immunity. Thus, our study reveals a regulatory mechanism by which pathogen effectors target a transcriptional complex to reprogram transcription.