DmAMP1, a plant defensin from Dahlia mercki and syringomycin E, a lipopeptide from Pseudomonas syringae pv. syringae are membrane interacting compounds with potent antifungal activities. Previous studies suggested that both require biosynthesis of sphingolipid mannosyldiinositolphosphoceramide [M(IP)2C] for yeast growth inhibition. To further determine the lipid requirements for antifungal action, additional genes that play roles in sensitivity towards these compounds were identified. Screening of a Saccharomyces cerevisiae deletion mutant library for increased DmAMP1-resistance revealed a novel sensitivity-conferring gene, namely SKN1. The skn1&Delta_upper; deletion mutant showed resistance to both DmAMP1 and syringomycin E. Sphingolipids from the skn1&Delta_upper; mutant were labeled with H332PO4, extracted and separated by one- and two-dimensional thin–layer chromatography, and the mutant was observed to lack M(IP)2C. Overexpression of the M(IP)2C biosynthesis gene IPT1 in skn1&Delta_upper; complemented the skn1 mutation, conferred sensitivity to both DmAMP1 and syringomycin E , and resulted in M(IP)2C levels comparable to the wild type. These results show that SKN1– together with IPT1 – is involved in the last step of sphingolipid biosynthesis, and they further emphasize the role of M(IP)2C in the action of DmAMP1 and syringomycin E .
Full conference title:
American Society for Microbiology General Meeting
- ASM 102nd (2002)