@article {Warnock015545, author = {Neil D. Warnock and Leonie Wilson and Juan V. Canet-Perez and Thomas Fleming and Colin C. Fleming and Aaron G. Maule and Johnathan J. Dalzell}, title = {ExoRNAi, a new tool to probe plant gene function exposes contrasting roles for sugar exudation in host-finding by plant pathogens}, elocation-id = {015545}, year = {2015}, doi = {10.1101/015545}, publisher = {Cold Spring Harbor Laboratory}, abstract = {Here we present a simple and rapid new method for RNAi-induced knockdown of genes in tomato seedlings, through treatment with an aqueous solution of double-stranded RNA (exoRNAi). The exoRNAi method is used to assess the involvement of tomato Sugar Transporter Protein genes, stp1 and stp2 on the root exudation of glucose, fructose and xylose; monosaccharide constituents of tomato root exudate. Plant parasitic nematodes (PPNs) are responsible for an estimated 12.3\% loss in crop production globally, which equates to financial losses of approximately {\textsterling}100 billion annually. Our data show that infective juveniles of the promiscuous PPN, Meloidogyne incognita are attracted to glucose and fructose, but not xylose. Glucose and fructose also agonise serotonergic stylet thrustning in M. incognita infective juveniles; a key parasitic behaviour necessary for invasion and parasitism of host plants. In contrast, infective juveniles of the selective Solanaceae PPN, Globodera pallida are not attracted to tested monosaccharides, nor do the monosaccharides stimulate stylet thrusting. We demonstrate that knockdown of both SlSTP1 and SlSTP2 in tomato seedlings by the exoRNAi method is robust and specific, and that corresponding reductions of glucose and fructose, but not xylose, in collected exudate correlate directly with reduced infectivity and stylet thrusting of M. incognita. Knockdown of SlSTP1 or SlSTP2 have no impact on the infectivity or stylet thrusting of G. pallida. The exoRNAi platform can underpin future efforts to understand the early stages of plant-pathogen interactions in tomato, and potentially other crop plants.}, URL = {https://www.biorxiv.org/content/early/2015/02/20/015545}, eprint = {https://www.biorxiv.org/content/early/2015/02/20/015545.full.pdf}, journal = {bioRxiv} }