Routtu, Jarkko

Helsingin yliopiston digitaalinen arkisto

universitet Univers of HelsinkiTyön laji A¡betets art LevelPro graduAika Datum Month and yearHelmikuu 1999Tiedekunta/Osasto FakultelSektion FacultyMatemaattis-luonnontieteellinenMuita tietoja Ovriga uppgifter Additionat informationSäilytyspaikka Förvaringsställe WheredepositedAvainsanat Nyckelord Keywordstransposons, transposable elements, Antl, Tanl, Vader, incompatibility, horizontal transfer.¡4 sP€R6/LLU5 utêERThe Aspergillus niger aggregate consists of asexually reproducing strains. The strains are incompatible with eachother. However they are highly variable on the basis of morphological, ribosomal and mitochondrial RFLP data.The research question was to detect possible recombination, which would explain the high variability of thestrains.There are two transposons in the A. niger aggregate. Transposons Antl and TanI. TanI has alsotransposable element Vader, which is cabable of transposing with a help of transposase of TanI, at the end of itscoding region. Vader itself is noncoding. These transposons were used to detect the possible recombination. Theresearch question for these transposons was; do the transposons exist in the sfudied strains and is there horizontaltransfer of the transposons.There were 25 strains from the A. niger aggrcgate from different origins. These strains were analysedalready on the basis of ribosomal and mitochondrial RFLPs and a three different genomic gene data. Theresearch was done by using PCR amplification, sequence analysis and southern hybridisation. The southernhybridisation failecl. Also the results, in the case of TanlMader, were not very informative. Antl sequences weresuccessfully PCR amplified and sequenced. Seven acquired sequences were analysed. They were aligned with thepublished Anl1 sequence and the phylogenetic tree of the Antl sequences was comp¿ued to the phylogenetic treeof a pgall gene. In the alignment differences between basepair composition of the sequences were detected. Acomparison between the phylogenetic trees of Antl and pgatr indicated a strong difference in the structure of thephylogenetic trees.The result strongly suggests; there is horizontal transfer of Antl transposons in the A. niger aggregate.Differences in the alignment showed that the structure of AntI is not conserved. Changes in, most likely,functioning sequences were detected. Some of the changes were silent and some changed the coded amino acidsequence. The phylogenetic tree comparison revealed identical Anl1 sequences located far from each other in thepgaII gene phylogenetic tree. A vertical transfer of transposon combined with a drift could have explained thepatchy distribution of AntI, but only if the Antl transposon would have been conservative. However, horizontaltransfer of the AntI transposon is the most probable explanation on the basis of the collected data.The final conclusion of horizontal transfer can be drawn only if additional information about the copynumber can be obtained through southern blotting. If transposons can exist only in low copy numbers in onestrain, the vertical transfer theory becomes more questionable than it already is.Tiivistelmä Referat AbstractSivumäärä Sidoantal Number of pages42Oppiaine Läroämne SubjectPerinnöllisyystiedeTyön nimi Arbetets titel Title :.Horizontal transfer of transposons in the Aspergillus niger aggregateTekijä Författa¡e AuthorRouttu, Jarkko Mika KaleviLaitos Institution DepartmentB iotieteiden laitos, perinnöllisyystieteen osasto

Horizontal transfer of transposons in the Aspergillus niger aggregate

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Helsingin yliopiston digitaalinen arkisto