Katileena Lohtander

Genetic diversity of green algal and cyanobacterial photobionts in Nephroma (Peltigerales)

Abstract Genetic diversity of green algal and cyanobacterial photobionts in Nephroma was examined by using nucleotide sequences of the ribosomal gene cluster. The lichens studied included both bipartite and tripartite species. There was very little variation in green algal-ITS sequences of N. arcticum and N. expallidum. Almost identical sequences were obtained from all thalli analysed and also from two tripartite Peltigera species. On the basis of SSU rDNA data the green algal photobionts of N. arcticum are closely related to the primary photobiont of P. britannica, and also to an endophytic alga of Ginkgo biloba. The SSU rDNA region of lichen-forming cyanobacteria was rather variable. A phylogenetic analysis indicated that the Nostoc specimens formed a monophyletic group and the strains were divided into two main groups. One clade included only cyanobionts of lichens, including those of all bipartite Nephroma species. The second group was genetically more heterogeneous and included mainly cyanobionts of terricolous cyanolichens, including those of both tripartite Nephroma species studied. The distinction between bi- and tripartite Nephroma species is significant as the mycobionts of tripartite species are not monophyletic. It implies that within Nephroma, evolutionary transitions between symbiosis types cannot have been achieved simply via an acquisition or loss of the green algal photobiont. As the Nostoc symbionts of bi- and tripartite species belong to different phylogenetic groups, an evolutionary change in green algal association has required a concurrent change in cyanobiont composition.

Photobiont Diversity in the Physciaceae (Lecanorales)

Abstract Newly designed algal-specific primers were used to amplify the ribosomal ITS region from 25 photobiont specimens from five lichenized fungi of the family Physciaceae (Lecanorales), Anaptychia ciliaris, Phaeophyscia orbicularis, Physcia caesia, P. tenella, and Physconia distorta. The obtained DNA sequences were then phylogenetically analyzed using parsimony jackknifing. The analyses indicated that the mycobionts associated with two photobiont species: Trebouxia impressa was found with all mycobionts, except Anaptychia ciliaris, which instead was associated with Trebouxia arboricola. In the jackknife tree, all Trebouxia arboricola sequences formed a monophyletic group with a high jackknife support. The Trebouxia impressa sequences also formed a well supported group, which in turn had some internal structure. The photobiont species is reported for the first time for Anaptychia ciliaris, Physcia caesia, and P. tenella. A phylogenetic tree for the photobiont, T. impressa, was compared to a phylogeny of the corresponding mycobionts, also based on ITS sequences. A combined analysis of the data from the photobiont and the data from the mycobiont was also performed. Several similarities were found in the tree topologies. The general similarity of the mycobiont and photobiont trees may indicate a coevolutionary history.

A phylogenetic study of Nephroma (lichen-forming Ascomycota)

The phylogeny of Nephroma was studied by nucleotide sequences of the mitochondrial ribosomal small subunit (mtSSU rDNA) and the internal transcribed spacers of the nuclear ribosomal repeat (ITS), together with chemical characters. The biological material included both bipartite and tripartite species and all Nephroma species native to northern Europe. Phylogenetic analyses demonstrated that all Nephroma species form a monophyletic group and that Peltigera constitutes the sister group to Nephroma. The two gene regions revealed qualitatively similar relationships within Nephroma and chemical characters had a minor impact on tree topologies. The results demonstrated that tripartite Nephroma species do not form a monophyletic group within the genus, this being in agreement with previous findings from bi- and tripartite Peltigera species. The results also indicated that N. resupinatum does not form a monophyletic group with all other bipartite Nephroma species but form a sister group to the studied Nephroma taxa. Furthermore, N. helveticum s. lat. is highly variable and seems to represent aggregates of closely related taxa. Also N. laevigatum and N. resupinatum are genetically variable. All European Nephroma species can be rapidly and accurately identified on the basis of their fungal ITS sequences. This will prove useful in ecological and environmental studies.

Transgenic Betula pendula expressing sugar beet chitinase IV forms normal ectomycorrhizae with Paxillus involutus in vitro

Abstract Mycorrhizal fungi contain chitin in their cell walls and may be influenced by transgenic chitinases. This study examined the ability of a transgenic tree, silver birch (Betula pendula Roth), constitutively expressing the sugar beet chitinase IV gene, to form ectomycorrhizae with Paxillus involutus (Batsch) Fr. Eight transgenic lines showing varying levels of sugar beet chitinase IV expression and the non-transgenic control plants were inoculated by P. involutus in vitro, and the morphology of the mycorrhizae, mycorrhization efficiency and shoot and root fresh weights were studied. All the transgenic birch lines were able to form normal ectomycorrhizae containing distinctive mantles and Hartig nets. The level of sugar beet chitinase IV expression had no significant influence on mycorrhizal colonization. The only significant differences between transgenic and control plants were detected in weight parameters. According to these results, the expression of sugar beet chitinase IV in silver birch is not deleterious to formation of ectomycorrhizae between birch and P. involutus.

New entities in Physcia aipolia-P-caesia group (Physciaceae, Ascomycetes) : an analysis based on mtSSU, ITS, group I intron and betatubulin sequences

We have revisited the phylogenetic evaluation of the Physcia aipolia—P. caesia lichen group (sect. Caesiae; Physciaceae, Lecanorales) in order to investigate whether new sequence data and extensive sampling can help us to understand the phylogenetic relationships in that group. We combined partial mtSSU DNA data with two previously used nuclear gene regions (betatubulin, ITS) and a group I intron. We also compared the resulting phylogenies with chemical and morphological characters. Altogether 52 specimens of the P. aipolia—P. caesia group were analysed. Direct optimization of the molecular data revealed several well-supported groups. Our results essentially agreed with those of the earlier studies, and we were able to confirm the independent taxonomic status of some controversial morphotaxa. We also discovered at least two distinct clades that potentially represent species new to science. A new nomenclatural combination, Physcia alnophila (Vain.) Loht., Moberg, Myllys & Tehler, is proposed.