The 124202 candidate effector of <i>Melampsora larici-populina</i> interacts with membranes in <i>Nicotiana</i> and <i>Arabidopsis</i>

<p><i>Melampsora larici-populina</i> (<i>Mlp</i>) is a parasitic fungus causing poplar leaf rust, a disease that threatens poplar plantations worldwide. Like other phytopathogens, <i>Mlp</i> translocates specialized proteins, called effectors, into host tissues and cells to eventually divert host resources. 124202 is a hypothetical <i>Mlp</i> effector selected through an <i>in silico</i> secretome analysis. It shares about 30% identity with the <i>M. lini</i> AvrM effector. Using heterologous systems, the objectives of this work were to assess if 124202 could mitigate <i>Arabidopsis</i> defence or potentiate <i>Pseudomonas</i> virulence and investigate its putative interaction partners in plants. Yeast two-hybrid screens identified three potential 124202 interactors in plants: lipoxygenase 2, synaptotagmin A and quinolinate synthase. Expression of a fluorescently tagged 124202 protein in <i>Nicotiana benthamiana</i> and <i>Arabidopsis thaliana</i> showed that it could be associated with membranes but may also be found in the cytoplasm of host cells. Bacterial infection assays in wild-type and 124202-expressing <i>Arabidopsis</i> lines indicate that 124202 does not alter the susceptibility of <i>Arabidopsis</i> to <i>Pseudomonas syringae</i> pv. <i>tomato</i> DC3000. Overall, our results suggest that the function of 124202 might involve vesicle-mediated trafficking but is unlikely to quantifiably contribute to the suppression of plant immunity.</p