Effect of GR24, a synthetic analogue of strigolactones, on gene expression of solopathogenic strain of Sporisorium reilianum

Sporisorium reilianum f.sp zeae, a basidiomycetous fungus belonging to Ustilaginaceae, is the causal agent of maize head smut. Its pathogenicity is initiated by fusion of two compatible sporidia which give rise to the formation of a dikaryotic pathogenic hyphe. In addition, pathogenic dimorphic diploid strains called solopathogens can be formed where no mating occurs. Strigolactones are the trace molecules in plant root exudates perceived by some fungi at subnanomolar concentrations that have been implicated in inducing spore germination in fungi. Cell respiration in fungal cells was measured through polarography and fluorescence assay. GR24, a synthetic analogue of strigolactones, induced a burst of cell respiration 1 h after adding GR24 (10 -7 M) that gradually decreased at 5 and 8 h after addition of GR24. Quantitative polymerase chain reaction (qPCR) analysis showed that transcription levels of genes involved in cell respiration and a 12 kDa heat shock protein were up-regulated 1 h after the addition of GR24 to a culture of the solopathogenic strain but no influence was observed on the other pathogenicity genes and on the culture morphology. These results suggest that strigolactones influence the rhizosphere and play a role in plant-microbe interactions