Development, optimisation and validation of molecular tools for assessment of biodiversity in forest trees

• Research unit: EU RFP
• Project number: 96.0307

Key words (English)

Genetic diversity; molecular markers; mitochondrial DNA; forest trees; Norway spruce

Alternative project number (English)

EU project number: BIO4CT96-0706

Research programs (English)

EU-programme: 4. Frame Research Programme - 4.1 Biotechnology

Short description (English)

See abstract

Partners and International Organizations (English)

14, coordinator: Bundesforschungsanst. Forst-und Holzwirtschaft (D)

Abstract (English)

Mitochondrial DNA is generally maternally inherited in plants and provides genetic information on population structures and population-level processes which is complementary to information obtained from nuclear DNA. The widespread application of mitochondrial DNA to population genetic studies, however, has been limited, largely as a result of the slow rate of sequence evolution in the molecule. We detected two polymorphic tandem repeats in mitochondrial DNA of Norway spruce and evaluated their utility for the study of the population genetic structure of Norway spruce. The two tandem repeats are located in the second intron of the nad1 gene and are composed of repeats of 32 and 34 bp, respectively. An efficient assay for sizing the tandem repeat region was developed which allowed accurate sizing of amplified DNA fragments in the size range of 712-891 bp in a single run on an automated sequencer.
The mode of inheritance of the mitochondrial tandem repeat region was analysed in the progenies of seven controlled crosses. All of the 132 offsprings revealed the size variant detected in the female parent, demonstrating maternal mitochondrial DNA inheritance in Norway spruce. For evaluating the utility of the tandem repeat region for the study of the population genetic structure of Norway spruce, variation in the repeat copy number was investigated in more than 1400 trees from 128 populations distributed over the species' entire natural range. Eighteen size variants were found and sequence determination demonstrated that 15 of the variants resulted from variation in the copy number of the two tandem repeats. The copy number of the 32 bp repeat varied from 0 to 7 and that of the 34 bp repeat from 0 to 6. The remaining 3 variants resulted from size variation at 5 sites in the sequences flanking the two tandem repeats. Most of the variants showed a distinct geographical distribution closely associated with ice-age refugia and postglacial migration of Norway spruce. The geographic distribution of these variants and phylogenetic analysis of the sequences flanking the two tandem repeats revealed the presence of two major gene pools in Norway spruce: a north-east European gene pool and a south-east/central European gene pool. Population differentiation of the repeat region was higher (Fst of about 60%) than that observed in a study of three polymorphic chloroplast microsatellites (Rst of about 10%), suggesting that pollen is the main agent for gene flow in Norway spruce (in co-operation with partner 07). The established marker thus appears to be informative for the study of the population history of Norway spruce and population-level processes. Furthermore, we identified several tandem repeats in the completely sequenced mitochondrial genomes of the angiosperm Arabidopsis thaliana and the liverwort Marchantia polymorpha indicating that mitochondrial tandem repeats occur in broad range of plant species and may serve as a novel marker for the study of the genetic structure of plant populations.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 96.0307