title: Interspecific variability of class II hydrophobin GEO1 in the genus Geosmithia.
abstract: The genus Geosmithia Pitt (Ascomycota: Hypocreales) comprises cosmopolite fungi living in the galleries built by phloeophagous insects. Following the characterization in Geosmithia species 5 of the class II hydrophobin GEO1 and of the corresponding gene, the presence of the geo1 gene was investigated in 26 strains derived from different host plants and geographic locations and representing the whole phylogenetic diversity of the genus. The geo1 gene was detected in all the species tested where it maintained the general organization shown in Geosmithia species 5, comprising three exons and two introns. Size variations were found in both introns and in the first exon, the latter being due to the presence of an intragenic tandem repeat sequence corresponding to a stretch of glycine residues in the deduced proteins. At the amino acid level the deduced proteins had 44.6 % identity and no major differences in the biochemical parameters (pI, GRAVY index, hydropathy plots) were found. GEO1 release in the fungal culture medium was also assessed by turbidimetric assay and SDS-PAGE, and showed high variability between species. The phylogeny based on the geo1 sequences did not correspond to that generated from a neutral marker (ITS rDNA), suggesting that sequence similarities could be influenced by other factors than phylogenetic relatedness, such as the intimacy of the symbiosis with insect vectors. The hypothesis of a strong selection pressure on the geo1 gene was sustained by the low values (<1) of non synonymous to synonymous nucleotide substitutions ratios (Ka/Ks), which suggest that purifying selection might act on this gene. These results are compatible with either a birth-and-death evolution scenario or horizontal transfer of the gene between Geosmithia species.
authors.affiliation: Dipartimento di Biologia, Università di Firenze, via Madonna del Piano 6, 50019 Sesto Fiorentino, FI, Italy; Dipartimento di Scienze delle Produzioni Agroalimentari e dell'Ambiente (DISPAA), Università di Firenze, via della Lastruccia 10, 50019 Sesto Fiorentino, FI, Italy. Electronic address: affabula@gmail.com.
authors.forename: Arcangela
authors.initials: A
authors.lastname: Frascella
authors.affiliation: Dipartimento di Biologia, Università di Firenze, via Madonna del Piano 6, 50019 Sesto Fiorentino, FI, Italy. Electronic address: p.bettini@unifi.it.
authors.forename: Priscilla P
authors.initials: PP
authors.lastname: Bettini
authors.affiliation: Institute of Microbiology of the ASCR, v.v.i, Videnská 1083, 142 20 Praha 4, Czech Republic. Electronic address: mkolarik@biomed.cas.cz.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Kolařík
authors.affiliation: Dipartimento di Scienze delle Produzioni Agroalimentari e dell'Ambiente (DISPAA), Università di Firenze, via della Lastruccia 10, 50019 Sesto Fiorentino, FI, Italy. Electronic address: cecilia.comparini@unifi.it.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Comparini
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche, Università di Firenze, Viale Morgagni 50, 50134 Florence, Italy. Electronic address: luigia.pazzagli@unifi.it.
authors.forename: Luigia
authors.initials: L
authors.lastname: Pazzagli
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche, Università di Firenze, Viale Morgagni 50, 50134 Florence, Italy. Electronic address: simone.luti@unifi.it.
authors.forename: Simone
authors.initials: S
authors.lastname: Luti
authors.affiliation: Dipartimento di Arboricoltura, Botanica e Patologia Vegetale, Sezione di Patologia Vegetale, Università di Napoli "Federico II", via Università 100, 80055 Portici, NA, Italy. Electronic address: felice.scala@unina.it.
authors.forename: Felice
authors.initials: F
authors.lastname: Scala
authors.affiliation: Dipartimento di Scienze delle Produzioni Agroalimentari e dell'Ambiente (DISPAA), Università di Firenze, via della Lastruccia 10, 50019 Sesto Fiorentino, FI, Italy. Electronic address: aniello.scala@unifi.it.
authors.forename: Aniello
authors.initials: A
authors.lastname: Scala
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000235:genetics* / Q000302:isolation & purification; D016000:Cluster Analysis; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D005091:Exons; D005656:Fungal Proteins / Q000235:genetics*; D014644:Genetic Variation; D007438:Introns; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer; D005656:Fungal Proteins; D008565:Membrane Proteins
keywords: Ascomycetes; Genetic diversity; Hypocreales; Intragenic tandem repeats; Protein evolution