Root-knot nematode effector MiMSP30 modulates cell wall integrity via promoter binding to promote pathogenicity

The formation of giant cells (GCs) is critical for root-knot nematode (RKN) parasitism and requires plant cell wall remodeling, yet the underlying mechanisms remain unclear. Here, we characterize a novel RKN effector, M. incognita putative esophageal gland cell secretory protein 30 (MiMSP30), which is specifically expressed in dorsal esophageal gland cells and significantly upregulated during RKN infection. MiMSP30 is suppressed by the biocontrol bacterium Bacillus cereus AR156 and promotes nematode penetration and development. Overexpression of MiMSP30 impaires cell wall integrity (CWI) and alters brassinosteroid (BR) signaling. Mechanistically, MiMSP30 binds to promoter regions of genes involved in CWI and BR signaling via five binding motifs, thereby modulating their transcription. Based on these findings, a nano-biopesticide was developed and demonstrated effective control against RKN. This study uncovers a novel mechanism underlying biocontrol action and reveals a new mode of RKN effector function, supporting the promising application of nanoscale pesticides engineered from pathogen effector biology.