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Amy M Brunner

Publications and source records attributed to Amy M Brunner.

8 recordsLinked to original sources
PubMed2006

CO/FT regulatory module controls timing of flowering and seasonal growth cessation in trees.

Forest trees display a perennial growth behavior characterized by a multiple-year delay in flowering and, in temperate regions, an annual cycling between growth and dormancy. We show here that the CO/FT regulatory module, which controls flowering time in response to variations in daylength in annual plants, controls flowering in aspen trees. Unexpectedly, however, it also controls the short-day-induced growth cessation and bud set occurring in the fall. This regulatory mechanism can explain the ecogenetic variation in a highly adaptive trait: the critical daylength for growth cessation displayed by aspen trees sampled across a latitudinal gradient spanning northern Europe.

Adaptation, Physiological↗
PubMed2006

Transgenic sterility in Populus: expression properties of the poplar PTLF, Agrobacterium NOS and two minimal 35S promoters in vegetative tissues.

Transgenic sterility is a desirable trait for containment of many kinds of transgenes and exotic species. Genetically engineered floral sterility can be imparted by expression of a cytotoxin under the control of a predominantly floral-tissue-specific promoter. However, many otherwise desirable floral promoters impart substantial non-floral expression, which can impair plant health or make it impossible to regenerate transgenic plants. We are therefore developing a floral sterility system that is capable of attenuating undesired background vegetative expression. As a first step towards this goal, we compared the vegetative expression properties of the promoter of the poplar (Populus trichocarpa Torr. & Gray) homolog of the floral homeotic gene LEAFY (PTLF), which could be used to impart male and female flower sterility, to that of three candidate attenuator-gene promoters: the cauliflower mosaic virus (CaMV) 35S basal promoter, the CaMV 35S basal promoter fused to the TMV omega element and the nopaline synthase (NOS) promoter. The promoters were evaluated via promoter::GUS gene fusions in a transgenic poplar hybrid (Populus tremula L. x P. alba L.) by both histochemical and fluorometric GUS assays. In leaves, the NOS promoter conveyed the highest activity and had a mean expression level 5-fold higher than PTLF, whereas the CaMV 35S basal promoter fused to the omega element and the CaMV 35S basal promoter alone directed mean expression levels that were 0.5x and 0.35x that of PTLF, respectively. Differential expression in shoots, leaves, stems and roots was observed only for the NOS and PTLF promoters. Strongest expression was observed in roots for the NOS promoter, whereas the PTLF promoter directed highest expression in shoots. The NOS promoter appears best suited to counteract vegetative expression of a cytotoxin driven by the PTLF promoter where 1:1 toxin:attenuator expression is required.

Amino Acid Oxidoreductases↗
PubMed2005

Genetic transformation: a powerful tool for dissection of adaptive traits in trees.

Plant transformation and regeneration systems have become indispensable parts of gene discovery and functional characterization over the last two decades. Adoption of transformation methods in studies of plant adaptation to natural environments has been slow. This is a result of poor genomic knowledge and inefficient transformation systems for species dominating terrestrial ecosystems, and logistical difficulties in conducting field tests of genetically engineered organisms. In trees, where long generation cycles, high background polymorphism, large sizes and outcrossing systems of mating make production of near-isogenic lines and large experiments difficult, transformation is an attractive alternative for establishing direct linkages between genes and adaptively significant phenotypes. Here, we outline the capabilities, challenges, and prospects for transformation to become a significant tool for studying the ecophysiological adaptation of trees to the environment. Focusing on poplars (genus Populus) as model system, we describe how transformation-based approaches can provide insights into the genes that control adaptive traits. The availability of the poplar genome sequence, along with its large expressed sequences tag (EST) databanks, facile transformation and rapid growth, enable reverse genetic approaches to be used to test virtually any hypothesis of gene function.

Adaptation, Physiological↗
PubMed2004

A Populus EST resource for plant functional genomics.

Trees present a life form of paramount importance for terrestrial ecosystems and human societies because of their ecological structure and physiological function and provision of energy and industrial materials. The genus Populus is the internationally accepted model for molecular tree biology. We have analyzed 102,019 Populus ESTs that clustered into 11,885 clusters and 12,759 singletons. We also provide >4,000 assembled full clone sequences to serve as a basis for the upcoming annotation of the Populus genome sequence. A public web-based EST database (POPULUSDB) provides digital expression profiles for 18 tissues that comprise the majority of differentiated organs. The coding content of Populus and Arabidopsis genomes shows very high similarity, indicating that differences between these annual and perennial angiosperm life forms result primarily from differences in gene regulation. The high similarity between Populus and Arabidopsis will allow studies of Populus to directly benefit from the detailed functional genomic information generated for Arabidopsis, enabling detailed insights into tree development and adaptation. These data will also valuable for functional genomic efforts in Arabidopsis.

Ecosystem↗
PubMed2004

Validating internal controls for quantitative plant gene expression studies.

BACKGROUND: Real-time reverse transcription PCR (RT-PCR) has greatly improved the ease and sensitivity of quantitative gene expression studies. However, accurate measurement of gene expression with this method relies on the choice of a valid reference for data normalization. Studies rarely verify that gene expression levels for reference genes are adequately consistent among the samples used, nor compare alternative genes to assess which are most reliable for the experimental conditions analyzed. RESULTS: Using real-time RT-PCR to study the expression of 10 poplar (genus Populus) housekeeping genes, we demonstrate a simple method for determining the degree of stability of gene expression over a set of experimental conditions. Based on a traditional method for analyzing the stability of varieties in plant breeding, it defines measures of gene expression stability from analysis of variance (ANOVA) and linear regression. We found that the potential internal control genes differed widely in their expression stability over the different tissues, developmental stages and environmental conditions studied. CONCLUSION: Our results support that quantitative comparisons of candidate reference genes are an important part of real-time RT-PCR studies that seek to precisely evaluate variation in gene expression. The method we demonstrated facilitates statistical and graphical evaluation of gene expression stability. Selection of the best reference gene for a given set of experimental conditions should enable detection of biologically significant changes in gene expression that are too small to be revealed by less precise methods, or when highly variable reference genes are unknowingly used in real-time RT-PCR experiments.

Analysis of Variance↗
PubMed2004

Poplar genome sequence: functional genomics in an ecologically dominant plant species.

In addition to their value for wood products, members of the genus Populus (poplars) provide a range of ecological services, including carbon sequestration, bioremediation, nutrient cycling, biofiltration and diverse habitats. They are also widely used model organisms for tree molecular biology and biotechnology. The sequencing of the poplar genome to an approximately 6x depth adds to a long list of important attributes for research. These include facile transformation, vegetative propagation, rapid growth, modest genome size and extensive expressed sequence tags. Here, we discuss how the genome sequence and transformability of poplar, together with its high levels of genetic and ecological diversity, are enabling new insights into the genetic programs controlling ontogeny, ecological adaptation and environmental physiology of trees.

Ecosystem↗
PubMed2003

Forestry's fertile crescent: the application of biotechnology to forest trees.

Relative to crop plants, the domestication of forest trees is still in its infancy. For example, the domestication of many crop plants was initiated some 10,000 years ago in the so-called 'Fertile Crescent' of the Middle East. By contrast, the domestication of forest trees for the purposes of producing more fibre began in earnest in the last half century. The application of biotechnology to forest trees offers a great potential to hasten the pace of tree improvement for desirable end uses. This review outlines some of the progress that has been made in the application of biotechnology to forest trees, and considers the prospects for biotechnologically based tree improvement in the future.

Journal Article↗