Abstract: Disclosed are isolated nucleic acids consisting essentially of RPW nucleotide sequences (especially RPW8 from Arabidopsis thaliana, and related homologues and other sequences e.g. from Brassica napus; B. oleracea). These encode a novel class of resistance polypeptides having an N-terminal transmembrane domain and a coiled coil domain and which is capable of recognising and activating in a plant into which said nucleic acid is introduced a specific defense response to challenge with a powdery mildew pathogen e.g. E. cichoracearum. Also provided are related products e.g. primers, polypeptides, transgenic plants having enhanced resistance, plus also processes for producing these, and methods of use.