Biomedical subjects

C Lind-Halldén

Publications and source records attributed to C Lind-Halldén.

4 recordsLinked to original sources

PubMed2007

The evolutionary history of the common chloroplast genome of Arabidopsis thaliana and A. suecica.

The evolutionary history of the common chloroplast (cp) genome of the allotetraploid Arabidopsis suecica and its maternal parent A. thaliana was investigated by sequencing 50 fragments of cpDNA, resulting in 98 polymorphic sites. The variation in the A. suecica sample was small, in contrast to that of the A. thaliana sample. The time to the most recent common ancestor (T(MRCA)) of the A. suecica cp genome alone was estimated to be about one 37th of the T(MRCA) of both the A. thaliana and A. suecica cp genomes. This corresponds to A. suecica having a MRCA between 10 000 and 50 000 years ago, suggesting that the entire species originated during, or before, this period of time, although the estimates are sensitive to assumptions made about population size and mutation rate. The data was also consistent with the hypothesis of A. suecica being of single origin. Isolation-by-distance and population structure in A. thaliana depended upon the geographical scale analysed; isolation-by-distance was found to be weak on the global scale but locally pronounced. Within the genealogical cp tree of A. thaliana, there were indications that the root of the A. suecica species is located among accessions of A. thaliana that come primarily from central Europe. Selective neutrality of the cp genome could not be rejected, despite the fact that it contains several completely linked protein-coding genes.

Arabidopsis↗

PubMed2003

Chloroplast DNA indicates a single origin of the allotetraploid Arabidopsis suecica.

DNA sequencing was performed on up to 12 chloroplast DNA regions [giving a total of 4288 base pairs (bp) in length] from the allopolyploid Arabidopsis suecica (48 accessions) and its two parental species, A. thaliana (25 accessions) and A. arenosa (seven accessions). Arabidopsis suecica was identical to A. thaliana at all 93 sites where A. thaliana and A. arenosa differed, thus showing that A. thaliana is the maternal parent of A. suecica. Under the assumption that A. thaliana and A. arenosa separated 5 million years ago, we estimated a substitution rate of 2.9 x 10(-9) per site per year in noncoding single copy sequence. Within A. thaliana we found 12 substitution (single bp) and eight insertion/deletion (indel) polymorphisms, separating the 25 accessions into 15 haplotypes. Eight of the A. thaliana accessions from central Sweden formed one cluster, which was separated from a cluster consisting of central European and extreme southern Swedish accessions. This latter cluster also included the A. suecica accessions, which were all identical except for one 5 bp indel. We interpret this low level of variation as a strong indication that A. suecica effectively has a single origin, which we dated at 20 000 years ago or more.

Arabidopsis↗

PubMed2002

Genetic variation in Arabidopsis suecica and its parental species A. arenosa and A. thaliana.

Random amplified polymorphic DNA (RAPD) markers were used to estimate the level of genetic variation in Swedish accessions of the allopolyploid Arabidopsis suecica and its parental species A. thaliana and A. arenosa. The results showed clear differences among the three species with respect to the level of variation. A. arenosa was highly variable, A. thaliana showed a moderate level of variation whereas A. suecica was much less variable than the two other species. An extended analysis covering 19 Swedish populations of A. suecica corroborated the low level of variation in this species, yet 16 unique phenotypes were observed. No isolation by distance was observed. When the genetic variation was partitioned among and within populations of A. suecica, the results showed that the majority of the variation (81%) occurred among populations. This result is interpreted as a strong indication that A. suecica is autogamous in nature.

Arabidopsis↗

PubMed2000

Primer mixtures in RAPD analysis.

RAPD (random amplified polymorphic DNA) is a multiplex marker system that conventionally uses single-primer PCR to amplify random DNA fragments. Because of its multiplex nature, it is frequently used in bulked segregant analysis (BSA). In view of the very large numbers of markers BSA often requires, we investigated the use of mixtures of primers as a method of increasing the number of markers available. Theoretically, if a single-primer reaction produces x bands on average, an unrestrained PCR process using a primers should produce xa2 bands. Initially, we investigated mixtures containing from one to five primers. The average number of products increased slightly from the single-primer to the multiple-primer case, whereas it was rather constant for the different multi-primer combinations. This deviation from the theoretical expectations, which we attribute to the effects of competition, shows mixtures of more than two primers to be inefficient. The properties of two-primer mixtures in which the proportions of the two primers were varied were also investigated. The intensities of most of the products were influenced by the proportions of the primers used to create the mixture. A good fit was obtained to a model in which the average competitive ability of a band is directly proportional to the probability of randomly obtaining the band-producing primer combination from the pool of primers. Using two-primer mixtures, a(a-1)/2 different two-primer mixtures can be produced. A comparison of different schemes for constructing the two-primer mixtures indicates that the degree of resampling is similar for all schemes. In conclusion, the use of two-primer mixtures is a simple but very powerful strategy in BSA as it can generate an extremely large number of markers.

DNA Primers↗