Protein elicitor AMEP412 suppressed rice blast caused by Magnaporthe oryzae through triggering plant immunity

Abstract

AMEP412 is a protein elicitor secreted by Bacillus subtilis, exhibiting the ability to trigger plant immunity. In this study, we assessed how AMEP412 induced disease resistance in rice seedlings against rice blast caused by Magnaporthe oryzae. First, the pathogen inoculation assay confirmed that pre-treatment with AMEP412 significantly reduced the lesion areas on rice leaves. Subsequently, the inner response of rice seedlings to protein-eliciting and pathogen infection were analysed, respectively. At 12 h post treatment (hpt) with AMEP412, early defense response was successfully triggered in rice leaves, including obvious accumulation of reactive oxygen species and activity increase of antioxidant enzymes (superoxide dismutase, catalase, and peroxidase). Real-time quantitative polymerase chain reaction analysis also verified the upregulation of antioxidant related genes. After M. oryzae infection, rice leaves pre-treated with AMEP412 exhibited a quicker and stronger defense reaction than those in the control. At 6 h post infection (hpi), a series of early defense response pathways were activated, including phenylpropanoid biosynthesis, ascorbate and aldarate metabolism, and cutin, suberine, and wax biosynthesis. At 12 hpi, the downstream defense response pathways began to dominate, such as plant hormone signal transduction, mitogen-activated protein kinase signaling, and plant-pathogen interaction. Further RT-qPCR verification of key genes in these pathways showed that the plant immunity system was successfully activated. We confirmed that AMEP412 could rapidly and effectively trigger the rice immunity system, resulting in reduced disease symptoms in M. oryzae-infected leaves, thereby providing a novel option for the biocontrol of rice blast.