Abstract

The formation of root surface penetration structures by both beneficial arbuscular mycorrhizal (AM) fungi and pathogenic oomycetes is dependent upon the presence of plant cutin monomers. Recent research using Medicago truncatula mutants found that plants which were defective in a GPAT (glycerol-3-phosphate acyltransferase), encoded by the gene RAM2 , have disrupted cutin monomer composition. RAM2 mutant plants are much more resistant to colonisation by both Phytophthora palmivora (oomycete pathogen) and Rhizophagus irregularis (AM fungi) while their overall development is unaffected. My hypothesis is that the function of RAM2 may be conserved in other plant species with regard to their interaction with filamentous microbes. If this is true, it may be possible to transfer this resistance principle to important crop species, i.e. resistance to Phytophthora infestans, which causes late blight, in tomato and potato. So far I have identified multiple homologues of MtRAM2 in tomato, potato and Nicotiana benthamiana and am currently applying a reverse genetics approach to investigate their effect on P. infestans infection whilst also checking for developmental effects. Early results are intriguing because when RAM2 homologues are silenced in N. benthamiana an increase in susceptibility to P. infestans is observed. In parallel, when a tomato RAM2 homologue is transiently overexpressed in N. benthamiana, leaves are more resistant to P. infestans.