title: Novel Introner-Like Elements in fungi Are Involved in Parallel Gains of Spliceosomal Introns.
abstract: Spliceosomal introns are key components of the eukaryotic gene structure. Although they contributed to the emergence of eukaryotes, their origin remains elusive. In fungi, they might originate from the multiplication of invasive introns named Introner-Like Elements (ILEs). However, so far ILEs have been observed in six fungal species only, including Fulvia fulva and Dothistroma septosporum (Dothideomycetes), arguing against ILE insertion as a general mechanism for intron gain. Here, we identified novel ILEs in eight additional fungal species that are phylogenetically related to F. fulva and D. septosporum using PCR amplification with primers derived from previously identified ILEs. The ILE content appeared unique to each species, suggesting independent multiplication events. Interestingly, we identified four genes each containing two gained ILEs. By analysing intron positions in orthologues of these four genes in Ascomycota, we found that three ILEs had inserted within a 15 bp window that contains regular spliceosomal introns in other fungal species. These three positions are not the result of intron sliding because ILEs are newly gained introns. Furthermore, the alternative hypothesis of an inferred ancestral gain followed by independent losses contradicts the observed degeneration of ILEs. These observations clearly indicate three parallel intron gains in four genes that were randomly identified. Our findings suggest that parallel intron gain is a phenomenon that has been highly underestimated in ILE-containing fungi, and likely in the whole fungal kingdom.
authors.affiliation: Laboratory of Phytopathology, Wageningen University, Wageningen, The Netherlands; Present address: UMR1345 IRHS-INRA, Beaucouzé, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Collemare
authors.affiliation: Laboratory of Phytopathology, Wageningen University, Wageningen, The Netherlands; Present address: Dyadic, Wageningen, The Netherlands.
authors.forename: Henriek G
authors.initials: HG
authors.lastname: Beenen
authors.affiliation: Evolutionary Phytopathology, CBS-KNAW Fungal Biodiversity Centre, Utrecht, The Netherlands.
authors.forename: Pedro W
authors.initials: PW
authors.lastname: Crous
authors.affiliation: Laboratory of Phytopathology, Wageningen University, Wageningen, The Netherlands.
authors.forename: Pierre J G M
authors.initials: PJ
authors.lastname: de Wit
authors.affiliation: Laboratory of Phytopathology, Wageningen University, Wageningen, The Netherlands; Present address: Dyadic, Wageningen, The Netherlands.
authors.forename: Ate
authors.initials: A
authors.lastname: van der Burgt
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000145:classification / Q000235:genetics*; D001483:Base Sequence; D004271:DNA, Fungal / Q000145:classification / Q000235:genetics; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000145:classification / Q000235:genetics*; D007438:Introns / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D017381:Spliceosomes / Q000235:genetics*
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins