Patrick A. Reeves

Evolutionary Conservation of the FLOWERING LOCUS C-Mediated Vernalization Response: Evidence From the Sugar Beet (Beta vulgaris)

In many plant species, exposure to a prolonged period of cold during the winter promotes flowering in the spring, a process termed vernalization. In Arabidopsis thaliana, the vernalization requirement of winter-annual ecotypes is caused by the MADS-box gene FLOWERING LOCUS C (FLC), which is a repressor of flowering. During the vernalization process, FLC is downregulated by alteration of its chromatin structure, thereby permitting flowering to occur. In wheat, a vernalization requirement is imposed by a different repressor of flowering, suggesting that some components of the regulatory network controlling the vernalization response differ between monocots and dicots. The extent to which the molecular mechanisms underlying vernalization have been conserved during the diversification of the angiosperms is not well understood. Using phylogenetic analysis, we identified homologs of FLC in species representing the three major eudicot lineages. FLC homologs have not previously been documented outside the plant family Brassicaceae. We show that the sugar beet FLC homolog BvFL1 functions as a repressor of flowering in transgenic Arabidopsis and is downregulated in response to cold in sugar beet. Cold-induced downregulation of an FLC-like floral repressor may be a central feature of the vernalization response in at least half of eudicot species.

The utility of aged seeds in DNA banks

The long-term utility of DNA banks is predicated on the stability of DNA during storage. The quality and yield of DNA extracted from seeds from four garden species, which varied in age from 1 to 135 years old, was used to examine the early stages of DNA degradation. Seeds that were 70 years old yielded high molecular weight DNA, which permitted amplification of a 650bp segment of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA and a 487bp segment of the plastid-encoded large subunit of rubisco (rbcL). DNA extracted from seeds estimated to be about 135 years old was degraded, but still permitted amplification when routine extraction procedures were used. The rbcL sequences obtained from c. 135-year-old cucurbit seed DNA were consistent with species identifications based on seed morphological features; however, ITS sequences from the same samples were determined to be of fungal origin. A comparison of our results with studies of DNA stability in leaf specimens suggested that DNA degraded within both tissues, but perhaps more slowly within seeds. Evidence that high-quality DNA can be extracted from old, non-viable seeds expands the utility of seed banks in preserving genetic resources.

wolfPAC: building a high-performance distributed computing network for phylogenetic analysis using 'obsolete' computational resources.

wolfPAC is an AppleScript-based software package that facilitates the use of numerous, remotely located Macintosh computers to perform computationally-intensive phylogenetic analyses using the popular application PAUP* (Phylogenetic Analysis Using Parsimony). It has been designed to utilise readily available, inexpensive processors and to encourage sharing of computational resources within the worldwide phylogenetics community.

Exploring the fate of mRNA in aging seeds: protection, destruction, or slow decay?

Aged soybean seeds show widespread cleavage of long mRNA transcripts with no particular relationship to transcript function, consistent with extant hypotheses of aging mechanisms.

Effect of error and missing data on population structure inference using microsatellite data

Missing data and genotyping errors are common in microsatellite data sets. We used simulated data to quantify the effect of these data aberrations on the accuracy of population structure inference. Data sets with complex, randomly-generated, population histories were simulated under the coalescent. Models describing the characteristic patterns of missing data and genotyping error in real microsatellite data sets were used to modify the simulated data sets. Accuracy of ordination, tree-based, and model-based methods of inference was evaluated before and after data set modifications. The ability to recover correct population clusters decreased as missing data increased. The rate of decrease was similar among analytical procedures, thus no single analytical approach was preferable. For every 1% of a data matrix that contained missing genotypes, 2–4% fewer correct clusters were found. For every 1% of a matrix that contained erroneous genotypes, 1–2% fewer correct clusters were found using ordination and tree-based methods. Model-based procedures that minimize the deviation from Hardy-Weinberg equilibrium in order to assign individuals to clusters performed better as genotyping error increased. We attribute this surprising result to the inbreeding-like nature of microsatellite genotyping error, wherein heterozygous genotypes are mischaracterized as homozygous. We show that genotyping error elevates estimates of the level of genetic admixture. Overall, missing data negatively impact population structure inference more than typical genotyping errors.