AUTHOR=Wang Ji , Shen Danyu , Ge Chengcheng , Du Yaxin , Lin Long , Liu Jin , Bai Tian , Jing Maofeng , Qian Guoliang , Dou Daolong 

TITLE=Filamentous Phytophthora Pathogens Deploy Effectors to Interfere With Bacterial Growth and Motility

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.581511

DOI=10.3389/fmicb.2020.581511

ISSN=1664-302X

ABSTRACT=<p><italic>Phytophthora</italic> comprises a group of filamentous plant pathogens that cause serious crop diseases worldwide. It is widely known that a complex effector repertoire was secreted by <italic>Phytophthora</italic> pathogens to manipulate plant immunity and determine resistance and susceptibility. It is also recognized that <italic>Phytophthora</italic> pathogens may inhabit natural niches within complex environmental microbes, including bacteria. However, how <italic>Phytophthora</italic> pathogens interact with their cohabited microbes remains poorly understood. Here, we present such an intriguing case by using <italic>Phytophthora</italic>–bacteria interaction as a working system. We found that under co-culture laboratory conditions, several <italic>Phytophthora</italic> pathogens appeared to block the contact of an ecologically relevant bacterium, including <italic>Pseudomonas fluorescence</italic> and a model bacterium, <italic>Escherichia coli</italic>. We further observed that <italic>Phytophthora sojae</italic> utilizes a conserved Crinkler (CRN) effector protein, PsCRN63, to impair bacterial growth. <italic>Phytophthora capsici</italic> deploys another CRN effector, PcCRN173, to interfere with bacterial flagellum- and/or type IV pilus-mediated motility whereas a <italic>P. capsici</italic>-derived RxLR effector, PcAvh540, inhibits bacterial swimming motility, but not twitching motility and biofilm formation, suggesting functional diversification of effector-mediated <italic>Phytophthora</italic>–bacteria interactions. Thus, our studies provide a first case showing that the filamentous <italic>Phytophthora</italic> pathogens could deploy effectors to interfere with bacterial growth and motility, revealing an unprecedented effector-mediated inter-kingdom interaction between <italic>Phytophthora</italic> pathogens and bacterial species and thereby uncovering ecological significance of effector proteins in filamentous plant pathogens besides their canonical roles involving pathogen–plant interaction.</p>