@article{clark_carbone_2008, title={Chloroplast DNA phylogeography in long-lived Huon pine, a Tasmanian rain forest conifer}, volume={38}, ISSN={["1208-6037"]}, DOI={10.1139/X07-209}, abstractNote={Genealogy based methods were used to estimate phylogeographic history for a Tasmanian endemic conifer, Huon pine ( Lagarostrobos franklinii (Hook. f.) Quinn). DNA from trees in eight populations was sequenced using three chloroplast primers (trnS–trnT, trnD–trnT, and psbC–trnS). Mean nucleotide diversity was low (π = 0.000 93 ± 0.000 06) from 892 base pairs of sequence, but varied in stands from 0.0 to 0.001 15. Two of the five haplotypes were widely distributed, but the most frequently occurring haplotype was found only in the western portion of the range. Population structure was highly significant among populations overall (GST= 0.261, where GSTis the coefficient of gene differentiation, and p ≤ 0.0001), and there were indications of significant isolation by distance (p ≤ 0.022). Populations exhibited the highest levels of differentiation between the southeastern and northwestern watersheds. Estimates of migration between populations obtained using both parametric and nonparametric methods indicated levels of gene flow consistent with an isolation by distance model. Nested clade analysis demonstrated a pattern of genetic diversity in Huon pine that is consistent with a history of range expansion. The exceptionally low level of nucleotide diversity, haplotype distribution, and paleoecological data are congruent with a history of long-term range reduction, population bottlenecks, and subsequent colonization events from refugial areas.}, number={6}, journal={CANADIAN JOURNAL OF FOREST RESEARCH}, author={Clark, Catherine M. and Carbone, Ignazio}, year={2008}, month={Jun}, pages={1576–1589} } @article{lu_sun_shi_clark_li_chiang_2005, title={Novel and mechanical stress-responsive microRNAs in Populus trichocarpa that are absent from Arabidopsis}, volume={17}, DOI={10.1105/tpc.105.033456}, abstractNote={Abstract MicroRNAs (miRNAs) are small, noncoding RNAs that can play crucial regulatory roles in eukaryotes by targeting mRNAs for silencing. To test whether miRNAs play roles in the regulation of wood development in tree species, we isolated small RNAs from the developing xylem of Populus trichocarpa stems and cloned 22 miRNAs. They are the founding members of 21 miRNA gene families for 48 miRNA sequences, represented by 98 loci in the Populus genome. A majority of these miRNAs were predicted to target developmental- and stress/defense-related genes and possible functions associated with the biosynthesis of cell wall metabolites. Of the 21 P. trichocarpa miRNA families, 11 have sequence conservation in Arabidopsis thaliana but exhibited species-specific developmental expression patterns, suggesting that even conserved miRNAs may have different regulatory roles in different species. Most unexpectedly, the remaining 10 miRNAs, for which 17 predicted targets were experimentally validated in vivo, are absent from the Arabidopsis genome, suggesting possible roles in tree-specific processes. In fact, the expression of a majority of the cloned miRNAs was upregulated or downregulated in woody stems in a manner consistent with tree-specific corrective growth against tension and compression stresses, two constant mechanical loads in trees. Our results show that plant miRNAs can be induced by mechanical stress and may function in one of the most critical defense systems for structural and mechanical fitness.}, number={8}, journal={Plant Cell}, author={Lu, S. F. and Sun, Y. H. and Shi, R. and Clark, C. and Li, L. G. and Chiang, V. L.}, year={2005}, pages={2186–2203} } @article{egertsdotter_zyl_mackay_peter_kirst_clark_whetten_sederoff_2004, title={Gene Expression during Formation of Earlywood and Latewood in Loblolly Pine: Expression Profiles of 350 Genes}, volume={6}, ISSN={1435-8603 1438-8677}, url={http://dx.doi.org/10.1055/s-2004-830383}, DOI={10.1055/s-2004-830383}, abstractNote={Abstract: The natural variability of wood formation in trees affords opportunities to correlate transcript profiles with the resulting wood properties. We have used cDNA microarrays to study transcript abundance in developing secondary xylem of loblolly pine (Pinus taeda) over a growing season. The cDNAs were selected from a collection of 75 000 ESTs that have been sequenced and annotated (http:web.ahc.umn.edubiodatansfpine). Cell wall thickness and climatic data were related to earlywood and latewood formation at different time points during the growing season. Seventy‐one ESTs showed preferential expression in earlywood or latewood, including 23 genes with no significant similarity to genes in GenBank. Seven genes involved in lignin synthesis were preferentially expressed in latewood. The studies have provided initial insights into the variation of expression patterns of some of the genes related to the wood formation process.}, number={6}, journal={Plant Biology}, publisher={Wiley}, author={Egertsdotter, U. and Zyl, L. M. and MacKay, J. and Peter, G. and Kirst, M. and Clark, C. and Whetten, R. and Sederoff, R.}, year={2004}, month={Nov}, pages={654–663} } @article{clark_wentworth_dm o'malley_2000, title={Genetic discontinuity revealed by chloroplast microsatellites in eastern North American Abies (Pinaceae)}, volume={87}, ISSN={["1537-2197"]}, DOI={10.2307/2656885}, abstractNote={Development of conservation strategies for Fraser fir (Abies fraseri) in the southern Appalachian Mountains depends in part on recognition of the extent to which Fraser fir is genetically distinct from the closely related balsam (A. balsamea) and intermediate (A. balsamea var. phanerolepis) fir. These sibling species have exhibited intergrading, clinal variation in morphological, chemical, and genetic characteristics in prior research. Chloroplast microsatellite markers were polymerase chain reaction amplified from genomic DNA samples of 78 individuals representing the geographic ranges of Fraser, balsam, and intermediate fir. Gene diversity levels at two loci ranged among taxa from 0.65 to 0.84. Allele frequencies demonstrated significant differentiation among taxa, with RST values of 0.36 and 0.10. Haplotype diversity and D2SH were highest for balsam fir and lowest for intermediate fir. A haplotype network analysis based on allele size distribution for the two loci revealed two distinct clusters of haplotypes and population‐specific haplotypes. Ninety‐two percent of the haplotypes in one cluster were from balsam fir and intermediate fir, and 84% of the haplotypes in the other cluster were from Fraser fir and intermediate fir. The genetic differentiation of chloroplast DNA markers provides justification for the recognition of Fraser fir as a distinct Management Unit (MU) for conservation purposes, regardless of its taxonomic classification.}, number={6}, journal={AMERICAN JOURNAL OF BOTANY}, author={Clark, CM and Wentworth, TR and DM O'Malley}, year={2000}, month={Jun}, pages={774–782} }