Bandara YMAY, Weerasooriya DK, Liu S, Little CR.

 Phytopathology. 2018 Feb 21. doi: 10.1094/PHYTO-12-17-0404-R. [Epub ahead of print]

Abstract

The cell wall degrading enzymes (CWDEs) secreted by necrotrophs are important virulence factors. Although not unequivocally demonstrated, it has been suggested that necrotrophs induce hosts to cooperate in disease development through manipulation of host CWDEs. The necrotrophic fungus, Macrophomina phaseolina (Tassi) Goid. (MP), causes charcoal rot disease in Sorghum bicolor (L.) Moench. An RNA-seq experiment was conducted to investigate the behavior of sorghum CWDEs encoding genes after MP inoculation. Results revealed MP's ability to significantly up-regulate pectin methylesterase-, polygalacturonase-, cellulase-, endoglucanase-, and glycosyl hydrolase-encoding genes in a charcoal rot susceptible sorghum genotype (Tx7000), but not in a resistant genotype (SC599). For functional validation, crude enzymes mixtures (CEM) were extracted from MP- and mock-inoculated charcoal rot resistant (SC599, SC35) and susceptible (Tx7000, BTx3042) sorghum genotype stalks. A gel diffusion assay (pectin substrate) revealed significantly increased pectin methylesterase activity in MP-inoculated Tx7000 and BTx3042. Polygalacturonase activity was determined using a ruthenium red absorbance assay (535 nm). Significantly increased polygalacturonase activity was observed in two susceptible genotypes after MP inoculation. The activity of cellulose degrading enzymes was determined using a 2-cyanoacetamide fluorimetric assay (excitation and emission maxima at 331 and 383 nm, respectively). The assay revealed significantly increased cellulose degrading enzyme activity in MP-inoculated Tx7000 and BTx3042. These findings revealed MP's ability to promote charcoal rot susceptibility in grain sorghum through induced host CWDEs.

See: https://www.ncbi.nlm.nih.gov/pubmed/29465007