Bacillus cereus AR156 suppresses the pathogenicity of root-knot nematode by disrupting MiMSP30 secretion, which is identified targeting host nuclear functions to alter genes expression involved in cell wall integrity and defense responses

t Previously, a number of microbes have been developed as potential bio-control agents against root-knot nematodes (Meloidogyne spp., RKNs), which are threatening the crop production worldwide. Lots of studies have been carried out to display the mechanism of bio-control agents, however, mostly are focusing on the activation of defense responses in hosts. Here, we uncovered a new effector MiMSP30 secreted by the model RKN M. incognita and suppressed by bio-control bacterium Bacillus cereus AR156. Through gain-of-function and loss-of-function analyses, MiMSP30 has been demonstrated to positively control RKN infection and development in plant roots. Transcripts associated with plant cell wall integrity (CWI) and basal defenses changed with the over-expressed MiMSP30 in plants, as well as the accumulation of phytohormones, brassinosteroid, salicylic acid and jasmonic acid, which participate in the signaling of CWI and basal defenses, resulting in the decreased CWI and defense responses in plants. Furthermore, the activities of MiMSP30 to bind promoter regions of part of genes mentioned above and regulate the transcripts of them were verified. Taking these together, it is suggested that bio-control bacterium AR156 down-regulated the novel effector, MiMSP30, to reduce the pathogenicity of M. incognita in plants during prevention and control, which reveals a new mechanism of bio-control against RKNs.