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Melampsora larici-populina (Mlp) is a parasitic fungus causing poplar leaf rust, a disease that threatens poplar plantations worldwide. Like other phytopathogens, Mlp translocates specialized proteins, called effectors, into host tissues and cells to eventually divert host resources. 124202 is a hypothetical Mlp effector selected through an in silico secretome analysis. It shares about 30% identity with the M. lini AvrM effector. Using heterologous systems, the objectives of this work were to assess if 124202 could mitigate Arabidopsis defence or potentiate Pseudomonas 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 Nicotiana benthamiana and Arabidopsis thaliana showed that it could be associated with membranes but may also be found in the cytoplasm of host cells. Bacterial infection...

Plants have evolved sophisticated defence mechanisms against pathogen infection, during which Resistance (R) proteins play a central role in recognizing pathogens and initiating downstream defence cascades. In Arabidopsis, the dominant mutant snc1 was previously identified that constitutively expresses P athogenesis- R elated(PR) genes and displays enhanced resistance against both bacterial and oomycete pathogens. A point mutation in this gene renders the encoded TIR-NB-LRR type R protein constitutively active without interaction with pathogens. Both suppressor screen and activation tagging approaches were used to identify regulators downstream of snc1. From these efforts, 15 complementation groups of m odifier o f s nc1 (mos) mutants were identified. We have cloned 11 of the mutations using map-based approaches, and have fully characterized mos2 through mos8. Analysis of the corresponding MOS genes and their protein products reveals a complicated signalling network downstream of R protein activa...

Specific polymerase chain reaction (PCR) primers were developed for the internal transcribed spacer (ITS) region of the rDNA gene of Inonotus tomentosus, the causal agent of tomentosus root rot of conifers. The primers were designed to specifically amplify DNA from I. tomentosus and allow its differentiation from Inonotus leporinus and from Phellinus pini s.l., which are morphologically very similar to I. tomentosus in culture. The PCR amplification was carried out successfully from DNA extracted from fruiting bodies and cultures and can potentially be used to detect the pathogen from environmental samples for survey and management purposes. The PCR assay was validated with 42 samples from seven coniferous hosts originating from eight provinces or states across the North American continent. No cross reaction was observed with DNA of several other species of the same genus, with Phellinus pini or with white spruce (Picea glauca), a conifer host of I. tomentosus. Phylogenetic analysis of the ITS region for ...