Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Transitory leaf starch is an important determinant of plant yield(Montana State University - Bozeman, College of Agriculture, 2011) Schlosser, Alanna Jane; Chairperson, Graduate Committee: Michael J. Giroux.Efficient allocation of photoassimilates from source to sink tissues is important for optimal plant growth and yield as relative source and sink strength drives growth potential of plant organs. A common method aimed at improving plant yield has been to modify enzymes important to storage compound biosynthesis in sink tissues such as seeds. As the rate limiting step in starch biosynthesis, ADP-glucose pyrophosphorylase (AGPase) has received much attention in this regard. Previously, overexpression of AGPase in seeds resulted in an enhanced yield phenotype in which both plant yield and biomass were increased. However, yield advantages were only observed under nonlimiting environmental resources. The objective of these studies was to 1) determine the importance of native leaf starch levels to the productivity and growth of maize and 2) target source strength by overexpressing AGPase in rice leaves. To determine the importance of native leaf starch levels in maize, field trials of BC 4F 2:3 plants segregating for the presence or absence of the agps-m1 mutation and leaf starch were conducted in Citra, Florida. The results clearly demonstrate the importance of normal leaf starch levels to maize productivity. The starchless agps-m1 plants were 6 to 13 cm shorter, flowered 2 to 3 days later, and had 30 percent lower seed yield than their wild type sisterlines. The impact of increased AGPase in rice leaves was then tested by overexpressing AGPase in rice leaves. Two expression constructs were used to transform rice cultivar Nipponbare, each containing a modified form of the maize endosperm AGPase large subunit sequence, Sh2r6hs, as well as the small subunit sequence, Bt2. Expression of the transgenes was under control of either the rice leaf AGPase small subunit promoter, Ags1, or native rice RuBisCO small subunit promoter, RBC. Expression of the transgenes under the RBC promoter is associated with significantly increased plant biomass. Our results indicate that it is possible to increase plant yield without increasing the rate of photosynthesis. Further, it indicates the possibility of manipulating plant yield through increasing AGPase activity in leaf tissue.Item Evolution of the molecular mechanisms of pheromone reception in European and Asian corn borer moths(Montana State University - Bozeman, College of Agriculture, 2010) Allen, Jean Elaine; Chairperson, Graduate Committee: Kevin Wanner.; Kevin W. Wanner, Andrew S. Nichols, Peggy L. Bunger, Stephen F. Garczynski, Charles E. Linn Jr., Hugh M. Robertson and Charles W. Luetje were co-authors of the article, 'Sex pheromone receptor specificity in the European corn borer moth, Ostrinia nubilalis' in the journal 'PLoS ONE' which is contained within this thesis.; Kevin W. Wanner was a co-author of the article, 'Asian corn borer pheromone binding protein 3, a candidate for evolving specificity to the 12-tetradecenyl acetate sex pheromone' in the journal 'Insect biochemistry and molecular biology' which is contained within this thesis.The insect order Lepidoptera includes more than 180,000 species and some of the most well known pests of food and fiber crops. Ninety-eight percent of lepidopteran species belong to a taxonomic group called the Ditrysia. Modern Ditrysia use long distance sex pheromones to facilitate mating. The European corn borer, Ostrinia nubilalis (ECB) is a well known pest of agricultural crops throughout North America and Western Europe. The European corn borer species exists as two different pheromone races. Females of the species produce, and males are attracted to different blends of the isomers (Z)-11-tetradecenyl acetate and (E)-11-tetradecenyl acetate. The closely related Asian corn borer (O. furnacalis, ACB) has evolved to use a pheromone blend that is unique among all Lepidoptera, (Z)- and (E)-12-tetradecenyl acetate. O. nubilalis and O.furnacalis species can be used as models to study pheromone evolution. Pheromones are detected at the periphery of the olfactory system by olfactory sensilla located on the antennae. Proteins involved in pheromone detection at the periphery include: odorant receptors, pheromone binding proteins, and sensory neuron membrane proteins. In this study, the coding sequences of seven odorant receptors, five pheromone binding proteins, and two sensory neuron membrane proteins were cloned from Asian and European (E and Z race) corn borer antennae. Five odorant receptors and two pheromone binding proteins were expressed at high levels in male corn borer antennae based on quantitative real-time PCR assays. Several odorant receptors were heterologously expressed in Xenopus laevis oocytes, and odorant receptor 6 was found to respond specifically to (Z)-11-tetradecenyl acetate in electrophysiological studies. The coding sequences of all fourteen genes were analyzed by computational and statistical methods to identify candidate genes that may play a role in the detection of the ACB pheromone blend. Odorant receptor 3 and pheromone binding protein 3 may have evolved specificity to 12-tetradecenyl acetates. Future studies will clarify the role of these proteins in the evolution of pheromone detection at the molecular level. An improved understanding of the evolution of pheromone detection may lead to new pheromone based controls for these economically damaging species.