Tuopų genties medžiai paprastoji drebulė Populus tremula ir smulkiadantė tuopa (kanadinė drebulė) Populus tremuloides yra vieni iš labiausiai paplitusių medžių Europoje bei Šiaurės Amerikoje. Šio tyrimo metu buvo išanalizuota dviejų Populus tremuloides and Populus tremula hibridų (augančių Lietuvoje, Kauno rajone) ir 50 jų palikuonių genetinė įvairovė bei giminingumas naudojantis atsitiktinai pagausintos polimorfinės DNR (RAPD) metodą. Šio darbo tikslas buvo nelaukiant hibridinių Populus medžių amžiaus brandos RAPD metodu įvertinti genetinę jų įvairovę ir giminingumą. Tyrimų vykdymui buvo iškelti uždaviniai: RAPD metodu nustatyti pasirinktų hibridinių drebulių genetinę įvairovę bei giminingumą, naudojamų RAPD reakcijoms pradmenų tinkamumą šiems drebulių hibridams, pradmenų informatyvumą. Įvertinta 50 hibridinės drebulės medžių palikuonių, regeneravusių mezginių kultūroje, genetinė įvairovė RAPD metodu. Hibridinės drebulės medžių palikuonių DNR polimorfizmo tyrimuose naudoti pradmenys Roth 170-02, Roth 170-03 ir Roth 170-10 pasižymėjo informatyvumu: po amplifikacijos elektroforegramose visada matėsi aiškūs įvairaus dydžio PGR produktai, ir atitinkamai gauta 17, 13 ir 10 fragmentų. Pradmenys Roth 170-01 ir 170-04 buvo mažai informatyvūs tirtų drebulių atveju. Pradmuo Roth 170-08 neinformatyvus, netinkamas tirtų drebulių RAPD analizei. Pagal RAPD rezultatus galima teigti, jog drebulių palikuonys buvo giminingesni nr.9 motininiam individui, nei nr.8 tėviniam individui. Genetiškai... [toliau žr. visą tekstą] / Trees of the poplar genus Populus tremula and Populus tremuloides are very common in Europe and North America. The genetic diversity and relation of two Populus tremuloides and Populus tremula hybrids (growing in Lithuania, Kaunas district) and 50 their offsprings were studied using random amplified polymorphic DNA method. The aim of this study was to estimate genetic relation and diversity of immature Populus trees in vitro and their parents using RAPD. The tasks of this study were: 1) evaluate genetic relation and diversity of selected hybrid aspens, 2) evaluate suitability and efficiency of used primers for these aspen hybrids. Primers used in this study Roth 170-02, Roth 170-03, and Roth 170-10 were informative. The results of electrophoresis using these primers were always discovered. Moreover there were identified a lot of fragments (40) using mentioned primers. Therefore these primers were effective in genetic relation and diversity studies of analysed P.tremula and P.tremuloides hybrid aspens. However primers Roth 170-01 and 170-04 in this case were little informative. The primer Roth 170-08 wasn’t informative, so it was unsuitable for RAPD analysis. According to RAPD results it was found that offsprings of aspens were more related to their mother individual (no.9) than to their father individual (no.8). The most closely RAPD based genetic distance found between individuals no.39 and no.40 (GDxy=0.05714), no.2 and no.20 (GDxy=0.10000), and no.7 and no.10 (GDxy=0.1025... [to full text]

Plant growth and development is largely controlled in regions of totipotential cells around the plant body called meristems. The well characterized shoot and root apical meristems are responsible for vertical growth, in which many key players have been well studied. Lateral (secondary) growth is controlled by the vascular and cork cambiums, which are much less understood. A rapid growth of interest in a new model angiosperm tree, poplar, has facilitated the study of the two cambiums, specifically into their regulation at the genomic and proteomic levels. This study describes recent work carried out to explore the genetic regulation of secondary growth in poplar. Two genes have been identified that were previously not associated with the process of secondary growth. The first, a gene lacking annotation (FM#2), was identified through the investigation of a mutant from an activation-tagged population of poplar. This mutant showed aberrant secondary growth, with an increase in the phloem:xylem ratio. It also developed a thick, rough bark, and was subsequently named corky. Constructs to recapitulate this phenotype have been produced to allow the link between the gene FM#2 and the corky phenotype to be firmly established. The second gene was identified through a reverse genetics strategy to test if the Arabidopsis shoot apical meristem regulator, CLAVATA1 also played a role in the regulation of the vascular cambium. When it was downregulated in Arabidopsis, a significant increase in secondary growth was observed. Antisense and hairpin-RNAi constructs were produced to attempt downregulation of the gene in poplar using both traditional Agrobacterium-mediated transformations, and the recently developed strategy of induced somatic sector analysis. / Thesis (Master, Biology) -- Queen's University, 2008-09-23 16:35:26.603

No description available.

Thesis (Ph.D.). / Written for the Dept. of Natural Resource Sciences. Title from title page of PDF (viewed 2009/06/08). Includes bibliographical references.

Thesis (M.S.)--Ohio University, March, 2004. / Includes bibliographical references (p. 30-38).

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2008. / Härtill 4 uppsatser.

Thesis (M.S.)--Ohio University, March, 2004. / Title from PDF t.p. Includes bibliographical references (p. 30-38)

Trees exhibit many unique aspects of plant biology, one of which is the formation of wood. Wood is one of the most important natural products with a multitude of applications. The formation of wood (xylogenesis) is a highly ordered developmental process involving the patterned division and differentiation of the vascular cambium into secondary xylem and phloem tissue types. The progression of xylogenesis developmental process requires differential gene expression across the different tissue types. The tight regulation of wood formation is mediated by genes that regulate cambial meristem differentiation and xylem cell fate. MicroRNAs (miRNAs) are a group of endogenous ~ 20 to 24 nt RNA molecules that down regulate gene expression at the post-transcriptional level. MicroRNAs have validated roles in developmental processes through the regulation of meristem cell differentiation and developmental patterning in plants. They have been shown to spatially regulate differential gene expression patterns at different developmental stages. Thus, the vascular cambium and its derivatives are excellent candidate tissues for miRNA discovery. The aim of this M.Sc. study was to isolate microRNAs from actively differentiating tissues of two tree species in order to determine possible gene regulatory networks involved in early meristem differentiation, tissue patterning and secondary vascular development. A small RNA library from two-month old in vitro Populus trichocarpa plantlets was constructed to identify putative miRNAs contributing to the early postembryonic development of trees. This library, in conjunction with computational prediction of poplar miRNA homologues and precursor secondary structures, was used to identify a total of 72 poplar miRNAs. Sixteen of these were putative novel miRNAs, belonging to nine new miRNA families. A genome-wide search identified 55 putative target genes for the newly identified miRNAs. The target genes had diverse biological roles in developmental events and maintenance of cellular homeostasis. A number of the predicted targets were involved in plant organ development such as leaf cell fate, floral organ development and meristem differentiation. Other targets were involved in response to hormones, such as growth regulating factors and signaling proteins. Additionally, several targets were related to cellular metabolic processes, such as protein modification and ubiquitination. By isolating miRNAs from developing poplar plantlets, we were able to suggest possible developmental programmes under the control of these molecules, possibly affecting early seedling development and growth. A similar approach was used to identify miRNAs from three differentiating vascular tissues of Eucalyptus grandis. Isolated small RNA sequences were used in a search against all available bacterial artificial chromosome (BAC) shotgun genomic sequences from an ongoing Eucalyptus camaldulensis genome sequencing initiative at the Kazusa DNA Research Institute in Japan. We were able to characterize the first Eucalyptus miRNAs, and identified 48 putative miRNAs grouping into thirteen gene families. Twenty of the miRNAs belong to five families previously identified in other plant species, whereas the remaining 28 miRNAs grouped into eight putative novel miRNA families. Searches of the Populus and Arabidopsis annotated genomes revealed 45 putative target genes for the new families. Targets of particular interest included transcription factors involved in cell fate determination, including a MADS-box transcription factor involved in xylem formation. Further targets included auxin signaling proteins and auxin response factors, which could play a significant role during auxin regulation of vascular development. Expression profiling of the putative miRNAs using quantitative RT-PCR revealed that a number of the miRNAs exhibited differential expression patterns across xylogenic and non-xylogenic tissues. One miRNA showed expression in a single vascular tissue, whereas others were expressed at varying levels across the vascular tissues. This observation indicates a possible role for these putative miRNAs during vascular development and differentiation in eucalypt trees. In this study we used a combination of small RNA library construction and computational prediction to identify microRNAs from two tree species. We identified a total of 120 putative miRNAs grouping into 31 families. Of these, 44 group into 17 putative novel tree-specific miRNAs. This study has allowed the identification of novel miRNAs from a unique set of tissues, and has contributed to the ever-growing number of plant-specific miRNAs. The results of this study further contribute to our expanding knowledge of the unique developmental process of vascular tissue differentiation of perennial woody plants such as Eucalyptus and Populus species. / Dissertation (MSc (Genetics))--University of Pretoria, 2006. / Genetics / unrestricted

Stomatal response of narrow leaf poplar (P. angustifolia; (PA)), balsam poplar (P. balsamifera; (PB)), cottonwood (P. deltoides; (PD)), and a P. angustifolia X P. balsamifera hybrid (PX) was studied in the field and in controlled environments. Mild water stress was occurring in both field studies, as evidenced by pre-dawn Ψ values of no less than -0.3 MPa; controlled experiments were more severe, with values dropping below -1.0 MPa. Stomatal conductance patterns differed for each species, and suggest that in terms of tolerating drought stress, PX > PA > PB > PD. These patterns were significantly influenced by microclimate conditions; severe conditions caused partial or complete stomatal closure, even in the presence of low water stress. Preconditioning plants through brief, repeated exposure to water stress resulted in stomatal closure at approximately -1.0 MPa, a higher level Ψ than is otherwise indicated for members of the genus Populus. It may thus be a valuable component of drought resistance for these species. Dieback studies indicated dissimilar patterns of dieback between PA and PB; PA experienced dieback on a large number of small branches while that of PB occurred on a small number of main branches. These results suggests that the drought stress response may differ between the two species, and may further indicate that the pattern of dieback is reflective of the physiological response to drought stress. / Thesis / Master of Science (MS)

Trees, like many other organisms, decrease their rate of metabolic activities to cope up with harsh environments. This stage of "dormancy" is marked by shedding of leaves and bud-set in deciduous trees. Recent studies have revealed the role of the circadian clock in synchronizing the timing of dormancy and physiology for conferring fitness in trees. To better understand the possible role of natural selection on circadian clock-related genes in climatic adaptation, I took a candidate gene approach, selecting circadian clock genes, some of which had been functionally validated, and others hypothesized, to identify signatures of natural selection in Populus trichocarpa and P. deltoides. Using both frequency spectrum based tests and tests of heterogeneity, I identified genetic variants deviating from selective neutrality. Results reveal that photoreceptors and dormancy regulator genes may have been the targets of natural selection. Nearly the same levels of selective constraints were found in different functional groups of genes irrespective of pleiotropy. Further, upstream regions of all genes showed high selective constraint, with some of them (FT-2, PIF-4, FRIGIDA) showing significantly higher variation than the other genes, hinting at the role of non-coding regulatory regions in local adaption. In some cases, the same genes in both species appeared as outliers, including PIF-6, FRI, FT-2, SRR1, TIC, and CO, which might reflect their common role in adaptation across species boundaries. All of these results indicate a complex nature of phenology regulation and local adaptation in Populus species with photoreceptors and dormancy regulator genes playing key roles. / Master of Science