Comparative proteome profiling of fusarium chlamydosporum and elucidation of pigment biosynthetic pathway under nitrogen stress

The main aim of this study was to understand the protein expression of F. chlamydosporum in two different medium composition in varying concentrations of nitrogen. The interesting phenomenon of producing diverse pigments by a single strain in different concentrations of Nitrogen made us further to explore the difference in the protein expression of the fungus when grown in these two media. For this, we had adopted non-gel-based method of protein separation by LC-MS/MS analysis followed by label free identification of proteins by SWATH analysis. The molecular and biological functions of each protein and their Gene Ontology annotations were analyzed by UniProt KB and KEGG pathway; the secondary metabolite pathways and the carbohydrate metabolic pathways were analyzed by DAVID bioinformatics tool. The positively regulated proteins biologically functioned for the secondary metabolite production in optimized medium were Diphosphomevalonate decarboxylase (terpenoid backbone biosynthesis), Phytoene synthase (carotenoid biosynthesis), 6,7-dimethyl-8-ribityllumazine synthase (riboflavin biosynthesis). The main characteristic change observed was that proteins related to carotenoid biosynthesis and terpenoid synthesis were not regulated in nitrogen limited medium. Except for the protein 6,7-dimethyl-8-ribityllumazine synthase, all the enzymes related to fatty acid biosynthesis and polyketide chain elongation were up regulated. Apart from the proteins related to secondary metabolite production, two novel proteins were found to be up regulated in Nitrogen Limited Medium; C-fem protein responsible for fungal pathogenesis and DAO domain containing protein which functions as a neuromodulator and catalyzes the synthesis of dopamine. SIGNIFICANCE: This particular strain of F. chlamydosporum of immense genetic and biochemical diversity represents an interesting example of a microorganism which can produce a variety of bioactive compounds and this can be exploited in various industries. The production of carotenoids and polyketides by this fungus when grown in the same media with different concentrations of Nitrogen has been published by us following which we analyzed the proteome sequence of the fungus in varying Nutrient conditions. Following the proteome analysis and expression, we could derive the pathway leading to the biosynthesis of varying secondary metabolites by the fungus which has not been published or studied so far.