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Cytogenetic and molecular characterization of Abies alba genome and its relationship with other members of Pinaceae family

Genome size, karyotype structure, heterochromatin distribution, position and number of ribosomal genes as well as ITS2 sequence of internal transcribed spacer (ITS) were analysed in silver fir (Abies alba Mill.). The analysis also included characterisation of Arabidopsis-type of telomeric repeats in silver fir and in the related species. The results were compared with results from other species of the Pinaceae family to evaluate phylogeny, chromosomal and molecular evolution in Pinaceae family. Integrated chromosomal data gave several insights in chromosome and karyotype evolution in Pinaceae family. Evolutionary trend for GC-rich heterochromatic blocks seems to involve rather loss of blocks that are not associated with rDNA. Similarly, numerous large blocks of interstitial plant telomeric repeats that are typical for all analyzed species of genus Pinus have not been observed in the evolutionary younger genera such as Abies, Picea and Larix. On contrary the majority of telomeric sequences in those three genera appeared confined to the chromosome ends. We confirmed current position of Abies and Tsuga in subfamily Abietoideae and position of Pinus in subfamily Pinoideae based on ITS2 sequences. Pseudotsuga is placed together with Larix into subfamily Laricoideae. We conclude that the current position of Picea genus in the subfamily Abietoideae should be reconsidered, and possibly Picea genus shoud be reclassified as separate subfamily Piceoideae as recently proposed.

silver fir; fluorescence in situ hybridization; fluorochrome banding; ITS; nuclear DNA content; 18S-5.8S-26S and 5S rDNA; telomeric repeats

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