Secretion of small non-coding RNA as new effectors in plant-nematode interaction

Abstract :

Root-knot nematodes (RKN) of the Meloidogyne genus are among the most destructive plant pathogens, causing significant agricultural losses amounting to billions of dollars each year. These plant-parasitic nematodes induce the formation of galls in root systems by inducing the dedifferentiation of few parenchyma cells into specialized giant, polynucleated, and hypermetabolic feeding cells that serve as nutrient sinks essential for their life cycle. This dramatic reprogramming of root cell identity is driven by Meloidogyne effectors secreted in root cells that manipulate host defense and gene expression. Since its discovery in the past decade, cross-kingdom RNA interference (RNAi) has emerged as a new mode of communication, based on the exchange of small non-coding RNAs (sncRNAs) that hijack RNA silencing pathways between interacting organisms. This raises the question of whether Meloidogyne-secreted sncRNAs play a role in the extensive gene expression reprogramming of root cells, facilitating the formation and maintenance of nematode-induced giant feeding cells. To investigate this, we performed immunoprecipitation of plant Argonaute 1 (AGO1) from infected roots followed by small RNA sequencing. Our analysis identified nine Meloidogyne-secreted microRNAs (miRNA) associated with Solanum lycopersicum AGO1. Similar experiments were also performed with Medicago truncatula and Arabidopsis thaliana infected roots to investigate if these secreted nematode miRNAs were specific of the host species. We identified two miRNAs secreted in all plant species which are known to be secreted by animal parasitic nematodes through vesicles. Using degradome sequencing, RNA sequencing, and computational target prediction algorithms, we identified the putative plant targets of these nematode secreted miRNAs whose cleavage activity of these target by min-miRNA was validated using dual-luciferase assay. Characterizing these secreted sncRNAs opens new perspectives on plant-RKN molecular dialogue and offers potential strategies for developing novel pest management approaches.