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

Abstract

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

Strigolactones as mediators between fungi and plants

“…(C) Pathogenic fungi interactions. In the preliminary data, SLs were not found to induce hyphal branching or respiration processes of the examined plant pathogens [30,34]. Even though there is no clear evidence that SLs are or are not a part of a host-pathogen signaling relation, it is an area that is interesting and undoubtedly tempting to explore, with some indications that SLs may be engaged in this process as signals preventing infection by promoting AM symbiosis.…”

“…Another study conducted in 2001 by Martinez et al [33] showed that fractions of maize root exudates could induce the transition of yeast to a hyphal form. In later research, Sabbagh [34] analyzed the transcriptome expression of a haploid strain of S. reilianum using different concentrations of GR24, and most of the expressed sequence tag (EST) after SL application was related to genes taking part in cell respiration processes. Exogenous GR24 effects on Ustilago maydis, a fungus causing smut on maize, induced genes involved in cell respiration at 1 h, increased the process at 5 h, and stopped it at 8 h postsupplementation; further analysis of cells induced at 8 h showed the lack of any candidate gene transcripts [34].…”

“…In later research, Sabbagh [34] analyzed the transcriptome expression of a haploid strain of S. reilianum using different concentrations of GR24, and most of the expressed sequence tag (EST) after SL application was related to genes taking part in cell respiration processes. Exogenous GR24 effects on Ustilago maydis, a fungus causing smut on maize, induced genes involved in cell respiration at 1 h, increased the process at 5 h, and stopped it at 8 h postsupplementation; further analysis of cells induced at 8 h showed the lack of any candidate gene transcripts [34]. Even if strigolactones do not affect the pathogenicity pathway of other fungi, they can still be used as compounds to prevent host plants from being infected through the promotion of arbuscular mycorrhiza formation.…”