The phaseolin (phas) promoter drives the copious production of transcripts encoding the protein phaseolin during seed embryogenesis but is silent in vegetative tissues when a nucleosome is positioned over its three phased TATA boxes. Transition from the inactive state in transgenic Arabidopsis leaves was accomplished by ectopic expression of the transcription factor PvALF (Phaseolus vulgaris ABI3-like factor), and application of abscisic acid (ABA). PvALF belongs to a family of seed-specific transcriptional activators that includes the maize viviparious1 (VP1) and the Arabidopsis abscisic acid-insensitive3 (ABI3) proteins. The major goal of the study is to gain insight to the regulation of seed-specific gene expression in three different aspects. First, since ABI3 (homolog of PvALF) is involved in ABA-mediated expression of several seed-specific protein genes in Arabidopsis, understanding its transcriptional regulation will provide insight to the mechanism by which PvALF expression is controlled. To achieve this, ABI3 promoter deletion analysis using either $-glucuronidase (gus) or green fluorescent protein (gfp) reporter gene fusions have identified various regulatory regions within the ABI3 promoter including two upstream activating sequences and a minimal seed specific expression region. In addition, a 405 bp 5' UTR was shown to play a negative role in ABI3 expression, possibly through post-transcriptional mechanisms. Second, placement of PvALF expression under control of an estradiol-inducible promoter permitted chronological ChIP analysis of changes in histone modifications, notably increased acetylation of H3-K9, as phas chromatin is remodeled (potentiated). A different array of changes (trimethylation of H3-K4) is associated with ABA-mediated activation. In contrast, H3-K14 acetylation decreased upon phas potentiation and increased on activation. Whereas decreases in histone H3 and H4 levels were detected during PvALF-mediated remodeling, slight increases occurred following ABA-mediated activation, suggesting the restoration of histone-phas interactions or the redeposition of histones in the phas chromatin. The observed histone modifications thus provide insight to the factors involved in euchromatinization and activation of a plant gene. Finally, ectopically expressed ABI5 and PvALF renders the activation of phas ABA-independent, suggesting ABI5 acts downstream of ABA during phas activation.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 121-134). Also available on the World Wide Web.

I studied the insect seed predator community on mesquite plants (Prosopis spp.) to investigate patterns of community composition in space and time, attempting to better understand the factors that led to the coexistence of many seed predator species on a single plant. This dissertation begins by testing the controversial species limits of Prosopis section Algarobía because hosts may act as environmental filters to insect seed predators. I found evidence for at least eight North American Prosopis species (section Algarobía). Second, I describe and add to the known natural history of 113 arthropod species among 315,174 individuals I collected from seedpod samples across the United States and Mexico. These samples included 187 trees from eight North American Prosopis species from section Algarobía and three from section Strombocarpa. Third, I examined reproductive timing in Prosopis and show that neighboring trees of the same species reproduce synchronously, whereas closely related species stagger reproduction. I found that photoperiod is the main cue that initiates flowering, but that multiple cues are involved. Thus, synchronous reproduction may act as an equalizing process that facilitates coexistence of seed predators in this system. Fourth, I tested for evidence of spatial and temporal niche partitioning among Prosopis seed predators. I found that the rank abundance of seed predators varies little over space and time, suggesting that this community exists in a homogeneous competitive environment. I also found that although a few species restrict the use of seeds to particular host plants or developmental stages of the pods, there is little evidence of niche partitioning. Finally, I looked for evidence of competition between seed predators and examined a number of factors that may allow for coexistence of these species. I found no evidence of interspecific competition or facilitation, suggesting that species somehow either avoid competition or that present patterns are the product of past competitive interactions. Natural enemies occur too sporadically to allow for apparent competition and I found no relationship between their occurrence or abundance and those of the seed predator species I studied. I found a positive correlation between rank abundance ability and fecundity, inconsistent with expectations of life-history or competitive-colonization trade-offs. Therefore, the only stabilizing process consistent with patterns found in this system is the niche regeneration hypothesis. I found that one seed predator species lays eggs most often away from both interspecific and intraspecific competitors, a pattern consistent with active avoidance as a second equalizing process within this system.

Revised

Soil erosion and vegetation destruction have reached serious proportions in disturbed areas of the montane grasslands of the Natal Drakensberg. Little is known of the inherent ability of indigenous grasses to produce viable seed and establish seedlings for rehabilitation programmes. This study examined the effects of fire and small-scale disturbance on the seedling dynamics of the dominant grass, Themeda triandra Forssk. Annual seed production of T. triandra increased with length of burning rotation, ranging from 21 seeds m⁻² in the annual winter burn to 485 seeds m⁻² in the five-year burn. High predation of seeds (70-98%) and low viability (37% in 15 month-old seeds) contributed to the poor representation of T. triandra in the seed bank when compared to the aboveground vegetation. Seedling densities and survival were monitored by mapping quadrats at six-weekly intervals from November 1986 to September 1989. Highest establishment of T. triandra was recorded in the biennial spring burn treatment (< 184 seedlings m⁻²). Microclimatic studies of the seedling environment demonstrated that increases in photosynthetically active radiation following burning, and high soil moisture associated with accumulation of litter, favour seedling establishment. The main constraint to seedling establishment was high mortality in winter which resulted in a 1% survival of seedlings of T. triandra during the three-year study. This indicates that in the fire-climax grasslands of the study, seedlings contribute little to the population structure. The most significant factor contributing to low survivorship is intraspecific competition between seedlings. Spacing of seedlings in rehabilitation programmes is therefore a critical factor in optimizing seedling establishment. Analysis of the fate of seeds of T. triandra between their production and establishment, showed that the main constraints for seedling establishment were predation, low viability and poor germination. A population model, based on transitions between seeds, seedlings and mature tufts, predicts that a biennial spring burn is the optimal treatment for maximising both seedling establishment and vegetative growth. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.

Soybean [Glycine max (L.) Merr.] seed is a major source of edible oil in the world and the main renewable raw material for biodiesel production in North America. Oil, which on average accounts for 20% of the soybean seed weight, is a complex quantitative trait controlled by many genes with mostly minor effects and influenced by environmental conditions. Because of its quantitative nature, the seed oil concentration may have an indirect effect on other economically important and agronomic traits such as seed yield and protein concentration. Increasing the oil concentration in soybean has been given more attention in recent years due to increasing demand for both edible oil and feedstock. To achieve this objective, it is important to understand the genetic control of the oil accumulation and its relationship with other traits. The main objectives of this thesis were to identify quantitative trait loci (QTL) and genes involved in oil biosynthesis in soybean. Two recombinant inbred line (RIL) populations were developed from crosses between moderately high oil soybean cultivars with high seed yield and protein concentration. In a population of 203 F3:6 RILs from a cross of ‘OAC Wallace’ and ‘OAC Glencoe’, a total of 11 genomic regions located on nine different chromosomes were identified as associated with oil concentration using multiple QTL mapping (MQM) and single-factor ANOVA. Among the 11 oil-associated QTL, four QTL were also validated in a population of 211 F3:5 RILs from a cross of ‘RCAT Angora’ and ‘OAC Wallace’. There were six oil QTL identified in this study that were co-localized with seed protein QTL and four for seed yield QTL. The oil-beneficial allele of the QTL tagged by marker Sat_020, on Chromosome 9, was positively associated with seed protein concentration. The oil-enhancing alleles at markers Satt001 and GmDGAT2B were positively correlated with seed yield. In this study, three sequence mutations were also discovered in either the coding or non-coding regions of three DGAT soybean genes (GmDGAT2B, GmDGAT2C, and GmDGAT1B) between ‘OAC Wallace’ and ‘OAC Glencoe’ that showed significant effects on some of the traits evaluated. GmDGAT2B showed significant association with seed oil and yield across different environments. The oil-favorable allele of the gene GmDGAT2B from ‘OAC Glencoe’ was also positively correlated with seed yield. GmDGAT2C was associated with seed yield, whereas GmDGAT1B showed significant effects on seed yield and protein concentration. However, neither of these two genes showed any association with seed oil. The yield-enhancing allele of GmDGAT1B showed negative association with protein concentration. The identification of oil QTL that were either positively associated with seed yield and protein or neutral to both traits and the development of new gene-based markers will facilitate marker-assisted breeding to develop high oil soybean cultivars with high yield and minimal effect on protein concentration. / Generous funding to conduct this research was provided by the Alternative Renewable Fuels II Program of the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and by the Grain Farmers of Ontario.

Common bean is a nutritionally and economically important food crop and a major source of dietary protein in many developing countries throughout the world. Seed coat colour and size in this crop are the main factors determining its marketability in different parts of the world. Flavonoid compounds that are responsible for seed coat colour in beans have been shown to have anti-oxidant, anti-proliferative, anti-tumor, anti-inflammatory, and pro-apoptotic activities. They also may enhance the resistance of beans to pest and disease. A better understanding of the relationships between seed coat colour and flavonoid metabolism in the seed coat may help breeders to select for more nutritionally-beneficial bean varieties. The objective of this research was to test the hypothesis that the genes determining colour in beans are structural and regulatory genes of the phenylpropanoid pathway. The map positions of phenylpropanoid genes were determined in two recombinant inbred populations. Segregation patterns of 18 phenylpropanoid pathway genes in the BAT93 × Jalo EEP 558 RIL population and five phenylpropanoid pathway genes in OAC Rex × SVM Taylor were used to place them on the linkage maps for these populations. Five out of 18 genes were mapped within 2-17 cM of colour gene loci in the BAT93 × Jalo EEP 558 RIL population. The sequences of central genes of the phenylpropanoid pathway were determined by sequencing 6 BAC clones selected with probes for two PAL genes, two CHS genes, DFR, and Myb. The functional annotations of the BAC clones were determined and the similarities between bean phenylpropanoid genes and their corresponding orthologs in other plant species were investigated. A recently developed approach of whole genome sequence comparison was utilized to compare the microsynteny of the sequenced BAC clones with regions of the soybean genome. The physical locations of BAC clones were verified on the bean genome and their counterpart locations on the soybean genome were confirmed. The results agreed with previous studies that indicated that bean genome segments have two homologous segments in soybean and confirmed the high degree of microsynteny that is shared between bean and soybean.

No description available.

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