Variation in telomeric repeats of Scots pine (Pinus sylvestris L.)

The shortening of telomeres, the specific structures at the end of the eukaryotic chromosomes, has been associated with ageing and loss of cell replication or regeneration capacity. The aim of this study was to determine the variation in telomeric repeats during the life-span of Scots pine (Pinus sylvestris L.) by studying different tissues and age groups ranging from immature embryos to cambium, buds, and needles of mature, 200-year-old trees. The telomeric repeats in Scots pine including interstitial and centromeric repeats ranged from 0.9 up to 25 kb, and true telomeres were evaluated to have a mean length of 19.3 kb (+/- SE 0.17). Telomeres were observed to shorten with increasing tissue differentiation, embryonal samples having the longest repeats with an average length of 21.1 (+/- 0.34) to 21.7 kb (+/- 0.42) and the needles having, on average, the shortest repeats of 18.1 kb (+/- 0.24). After germination, ageing per se had no significant effect on the length of telomeric repeats in cambium, bud, or needle tissues. In the older trees (50-200 years of age), the telomeres in stem cambium showed shortening towards the tree top. This is the first observation on such a position-related variation in telomeric repeats. Finally, there was a remarkable genotypic variation in the length of telomeric repeats, and this was consistent over the tissue types. In the small number of tested donor trees, the genotypic differences were not related to regeneration ability in tissue culture.