Contrasting carbon metabolism in saprotrophic and pathogenic microascalean fungi from Protea trees

Protea-associated Knoxdaviesia species grow on decaying inflorescences, yet are closely related to plant pathogens such as Ceratocystis albifundus. C. albifundus also infects Protea, but occupies a distinct niche. We investigated substrate utilization in two Knoxdaviesia saprotrophs, a generalist and a specialist, and the pathogen C. albifundus by integrating phenome and whole-genome data. On shared substrates, the generalist grew slightly better than its specialist counterpart, alluding to how it has maintained its Protea host range. C. albifundus grew on few substrates and had limited cell wall-degrading enzymes. It did not utilize sucrose, but may prefer soluble oligosaccharides. Nectar monosaccharides are likely important carbon sources for early colonizing Knoxdaviesia species. Once the inflorescence ages, they could switch to degrading cell wall components. C. albifundus likely uses its limited cell wall-degrading arsenal to gain access to plant cells and exploit internal resources. Overall, carbon metabolism and gene content in three related fungi reflected their ecological adaptations.Supplementary File 1: Table S1, List of BioLog carbon sources tested.Supplementary File 2: Tables S2 and S3, KEGG categories and unique carbon-metabolising enzymes identified in the Knoxdaviesia and Ceratocystis albifundus proteomes.Supplementary File 3: Tables S4 and S5, Families of carbohydrate-active enzymes (CAZymes) identified in Knoxdaviesia and Ceratocystis albifundus proteomes.Supplementary File 4: Figures S1-S5,Growth curves and predicted carbohydrate utilization pathways in Knoxdaviesia and Ceratocystis albifundus.The National Research Foundation (NRF) and the Department of Science and Technology (DST)-NRF Centre of Excellence in Tree Health Biotechnology.http://www.journals.elsevier.com/fungal-ecology2018-12-30hj2017Forestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog