The Cereal Phytopathogen Sporisorium Reilianum is Able to Infect the Non-Natural Host Arabidopsis Thaliana

We analyzed the infection of the model plant Arabidopsis thaliana by the basidiomycete phytopathogen of cereals Sporisorium reilianum in order to use it as an experimental pathosystem model. Sterile plantlets of A. thaliana were grown on MS solid medium, and inoculated with haploid strains or mixtures of sexually compatible S. reilianum strains. Inoculated plants showed growth of filaments within their tissues, size reduction, a drastic increase in the formation of lateral roots, and a high production of plant pigments. Although symptoms were more severe in plants infected with sexually compatible strains, no spores were formed by the fungus. Among the pigments accumulated in the stunted plants we identified the anthocyanins cyanidin, cyanidin 3-glucoside, malvidin and pelargonidin. Congruently, the anthocyanin biosynthesis genes: chalcone synthase (CHS, AT5G13930) and dihydroflavonol reductase (DFR, AT5G42800) were over-expressed. The three genes encoding flavin monooxygenases: YUCCA7 (YUC7, AT2G33230), YUCCA8 (YUC8, AT4G28720), and YUCCA9 (YUC9, AT1G04180), and the transcription factor Jagged Lateral Organs (JLO, AT4G00220), all of them involved in the biosynthesis of auxins specific for root development, were also positively regulated. These data provide evidence that both haploid and the mixture of sexually compatible strains of S. reilianum can infect plants of A. thaliana; evidencing the usefulness of this pathosystem for the study of the genetic and metabolic reactions involved in S. reilianum virulence.