Cyanobiont specificity in some Nostoc‐containing lichens and in a Peltigera aphthosa photosymbiodeme

Abstract

The cyanobacterial symbionts in some Nostoc-containing lichens were investigated using the nucleotide sequence of the highly variable cyanobacterial tRNA Leu (UAA) intron. When comparing different Nostoc-containing lichens, identical intron sequences were found in different samples of the same lichen species collected from two remote areas. This was true for all species where this comparison was made (Peltigera aphthosa (L.) Willd., P. canina (L.) Willd. and Nephroma arcticum (L.) Torss.). With one exception, a specific intron sequence was never found in more than one lichen species. However, for two of the species, Peltigera aphthosa and Nephroma arcticum, two different cyanobionts were found in different samples. By examining a P. aphthosa photosymbiodeme it could be shown that the same Nostoc is present in both bipartite and tripartite lobes of this lichen. It is thus possible for one cyanobiont\Nostoc to form the physiologically different symbioses that are found in bipartite and tripartite lichens. The connection between photobiont identity and secondary chemistry is discussed, as a correlation between differences in secondary chemistry and different cyanobionts\Nostocs in the species Peltigera neopolydactyla (Gyeln.) Gyeln. was observed. It is concluded that more knowledge concerning the photobiont will give us valuable information on many aspects of lichen biology.

Genetic Diversity of Nostoc Symbionts Endophytically Associated with Two Bryophyte Species

“…Amplification and sequencing were performed as previously described by Paulsrud and Lindblad (12) for samples collected in 1996 and 1998 or by Paulsrud et al (15) for samples collected in 2000. In agreement with previous work using the same approach on both cycad and lichen symbioses (3,12,13,14), differences in the nucleotide sequences were principally restricted to the intron's first variable region which could be divided into blocks of 7 nucleotides. The differences in intron size may be attributable to loss or acquisition of such blocks (Fig.…”

“…A similar pattern has also been detected in the cyanolichen Peltigera venosa, which may have different Nostoc strains in different colonies from a single thallus (14). Other cyanolichens have generally shown higher levels of specificity (12,13,14).…”

“…Several cyanobacterial colonies from each bryophyte thallus were used directly in PCRs with primers specific for the tRNA Leu gene. This intron has been widely used to examine questions of diversity and phylogeny in cyanobacteria (3,11,12,13,14) and in diverse plant groups, including liverworts (22), making it an appropriate tool for our work.…”

Fasciclin Domain Proteins Are Present in Nostoc Symbionts of Lichens

“…From these studies we established that there is great specificity in the examined lichen species (11,12). One Nostoc type is found not only in one thallus, but in many cases in thalli collected from remote areas (11,12). The fact that there is no Nostoc heterogeneity in one thallus makes it possible to perform experiments on freshly isolated symbionts without artifacts caused by mixed populations of Nostoc cells in the isolated cells.…”

“…From these studies we established that there is great specificity in the examined lichen species (11,12). One Nostoc type is found not only in one thallus, but in many cases in thalli collected from remote areas (11,12).…”