Transcriptional effects of carbon and nitrogen starvation on Ganoderma boninense, an oil palm phytopathogen

Abstract

Background Ganoderma boninense is a phytopathogen of oil palm, causing basal and upper stem rot diseases. Methods The genome sequence was used as a reference to study gene expression during growth in a starved carbon (C) and nitrogen (N) environment with minimal sugar and sawdust as initial energy sources. This study was conducted to mimic possible limitations of the C-N nutrient sources during the growth of G. boninense in oil palm plantations. Results Genome sequencing of an isolate collected from a palm tree in West Malaysia generated an assembly of 67.12 Mb encoding 19,851 predicted genes. Transcriptomic analysis from a time course during growth in this starvation media identified differential expressed genes (DEGs) that were found to be associated with 30 metabolic pathways. During the active growth phase (Day2), 27 DEGs related to four pathways, including secondary metabolite biosynthesis, carbohydrate metabolism, glycan metabolism and mycotoxin biosynthesis. G. boninense genes involved in the carbohydrate metabolism pathway that contribute to the degradation of plant cell walls were up-regulated. Interestingly, several genes associated with the mycotoxin biosynthesis pathway were identified as playing a possible role in pathogen-host interaction. Several genes associated with mycotoxin biosynthesis were associated with pathogen-host interactions. In addition, metabolomics analysis revealed six metabolites, maltose, xylobiose, glucooligosaccharide, glycylproline, dimethylfumaric acid and arabitol that were up-regulated on Day2 of the time course. Conclusions This study provides information on genes expressed by G. boninense in metabolic pathways that may play a role in the initial infection of the host.