A novel <i>Meloidogyne graminicola</i> effector, MgGPP, is secreted into host cells and undergoes glycosylation in concert with proteolysis to suppress plant defenses and promote parasitism

Abstract

<div><p>Plant pathogen effectors can recruit the host post-translational machinery to mediate their post-translational modification (PTM) and regulate their activity to facilitate parasitism, but few studies have focused on this phenomenon in the field of plant-parasitic nematodes. In this study, we show that the plant-parasitic nematode <i>Meloidogyne graminicola</i> has evolved a novel effector, MgGPP, that is exclusively expressed within the nematode subventral esophageal gland cells and up-regulated in the early parasitic stage of <i>M</i>. <i>graminicola</i>. The effector MgGPP plays a role in nematode parasitism. Transgenic rice lines expressing MgGPP become significantly more susceptible to <i>M</i>. <i>graminicola</i> infection than wild-type control plants, and conversely, <i>in planta</i>, the silencing of MgGPP through RNAi technology substantially increases the resistance of rice to <i>M</i>. <i>graminicola</i>. Significantly, we show that MgGPP is secreted into host plants and targeted to the ER, where the <i>N</i>-glycosylation and C-terminal proteolysis of MgGPP occur. C-terminal proteolysis promotes MgGPP to leave the ER, after which it is transported to the nucleus. In addition, <i>N</i>-glycosylation of MgGPP is required for suppressing the host response. The research data provide an intriguing example of <i>in planta</i> glycosylation in concert with proteolysis of a pathogen effector, which depict a novel mechanism by which parasitic nematodes could subjugate plant immunity and promote parasitism and may present a promising target for developing new strategies against nematode infections.</p></div