title: Saprophytic and pathogenic fungi in the Ceratocystidaceae differ in their ability to metabolize plant-derived sucrose.
abstract: BACKGROUND
  Proteins in the Glycoside Hydrolase family 32 (GH32) are carbohydrate-active enzymes known as invertases that hydrolyse the glycosidic bonds of complex saccharides. Fungi rely on these enzymes to gain access to and utilize plant-derived sucrose. In fungi, GH32 invertase genes are found in higher copy numbers in the genomes of pathogens when compared to closely related saprophytes, suggesting an association between invertases and ecological strategy. The aim of this study was to investigate the distribution and evolution of GH32 invertases in the Ceratocystidaceae using a comparative genomics approach. This fungal family provides an interesting model to study the evolution of these genes, because it includes economically important pathogenic species such as Ceratocystis fimbriata, C. manginecans and C. albifundus, as well as saprophytic species such as Huntiella moniliformis, H. omanensis and H. savannae.
  
  
  RESULTS
  The publicly available Ceratocystidaceae genome sequences, as well as the H. savannae genome sequenced here, allowed for the identification of novel GH32-like sequences. The de novo assembly of the H. savannae draft genome consisted of 28.54 megabases that coded for 7 687 putative genes of which one represented a GH32 family member. The number of GH32 gene family members appeared to be related to the ecological adaptations of these fungi. The pathogenic Ceratocystis species all contained two GH32 family genes (a putative cell wall and a putative vacuolar invertase), while the saprophytic Huntiella species had only one of these genes (a putative cell wall invertase). Further analysis showed that the evolution of the GH32 gene family in the Ceratocystidaceae involved transposable element-based retro-transposition and translocation. As an example, the activity of a Fot5-like element likely facilitated the assembly of the genomic regions harbouring the GH32 family genes in Ceratocystis.
  
  
  CONCLUSIONS
  This study provides insight into the evolutionary history of the GH32 gene family in Ceratocystidaceae. Our findings suggest that transposable elements shaped the evolution of the GH32 gene family, which in turn determines the sucrolytic activities and related ecological strategies of the Ceratocystidaceae species that harbour them. The study also provides insights into the role of carbohydrate-active enzymes in plant-fungal interactions and adds to our understanding of the evolution of these enzymes and their role in the life style of these fungi.
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. magriet.vandernest@fabi.up.ac.za.
authors.forename: M A
authors.initials: MA
authors.lastname: Van der Nest
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. emma.steenkamp@fabi.up.ac.za.
authors.forename: E T
authors.initials: ET
authors.lastname: Steenkamp
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. alistair.mctaggart@fabi.up.ac.za.
authors.forename: A R
authors.initials: AR
authors.lastname: McTaggart
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. conrad.trollip@fabi.up.ac.za.
authors.forename: C
authors.initials: C
authors.lastname: Trollip
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. tracy.godlonton@fabi.up.ac.za.
authors.forename: T
authors.initials: T
authors.lastname: Godlonton
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. elre.sauerman@fabi.up.ac.za.
authors.forename: E
authors.initials: E
authors.lastname: Sauerman
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. danielle.roodt@fabi.up.ac.za.
authors.forename: D
authors.initials: D
authors.lastname: Roodt
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. kershney.naidoo@fabi.up.ac.za.
authors.forename: K
authors.initials: K
authors.lastname: Naidoo
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. martin.coetzee@fabi.up.ac.za.
authors.forename: M P A
authors.initials: MP
authors.lastname: Coetzee
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. markus.wilken@fabi.up.ac.za.
authors.forename: P M
authors.initials: PM
authors.lastname: Wilken
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. mike.wingfield@fabi.up.ac.za.
authors.forename: M J
authors.initials: MJ
authors.lastname: Wingfield
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Pretoria, 0028, South Africa. brenda.wingfield@fabi.up.ac.za.
authors.forename: B D
authors.initials: BD
authors.lastname: Wingfield
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D002473:Cell Wall / Q000201:enzymology / Q000378:metabolism; D004251:DNA Transposable Elements; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D010944:Plants / Q000737:chemistry; D016415:Sequence Alignment; D013395:Sucrose / Q000378:metabolism*
chemical_list: D004251:DNA Transposable Elements; D013395:Sucrose; D006026:Glycoside Hydrolases