Theses and Dissertations at Montana State University (MSU)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/732
Browse
3 results
Search Results
Item Disease control and plant defense pathways induced by Bacillus mojavensis isolate 203-7 and Bacillus mycoides isolate BmJ(Montana State University - Bozeman, College of Agriculture, 2008) Neher, Oliver Thomas; Chairperson, Graduate Committee: Barry J. Jacobsen.The objective of this study was to investigate the plant defense pathways induced by Bacillus mojavensis isolate 203-7 (203-7) and B. mycoides isolate BmJ (BmJ) and to test their ability to control fungal pathogens on tomato and cucumber by means of systemic acquired resistance (SAR). An Arabidopsis thaliana mutant - Botrytis cinerea pathosystem was used to investigate plant defense pathways activated by 203-7 and BmJ. A. thaliana wild type (Col-0), ein2-1, jar1-1, NahG, ndr1-1/npr1-2, and npr1-1 mutants were induced by application of bacilli, distilled water, or chemical inducers. Both bacilli reduced disease severity on wild type and NahG mutants, but provided no reduction on jar1-1, indicating that induction was salicylic acid (SA) independent but jasmonic acid (JA) dependent. 203-7 induced plants had lower disease severity on npr1-1 and ein1-2 mutants but were equivalent to buffer controls on jar1-1 mutants. BmJ did not decrease disease severity on npr1-1, jar1 or ein2-1 mutants. Enzyme assays confirmed the induction of chitinase, beta-1,3-glucanase, and superoxide dismutase by 203-7 and BmJ. These results demonstrate that induction by 203-7 is JA dependent and NPR1 independent. BmJ is SA independent but NPR1 and JA/ethylene dependent. Bacilli were tested for their ability to control B. cinerea grey mold on hydroponically grown greenhouse tomatoes and Glomerella cingulata var. orbiculare on cucumber by means of SAR. Weekly foliar applications of bacilli were able to significantly (a=0.05) reduce the severity of grey mold leaf lesions and to reduce the area under the disease progress curve (AUDPC) calculated for seven Botrytis stem canker ratings. Chitinase, beta-1,3-glucanase, and SOD activity of apoplastic fluids were not significantly (a=0.05) increased by the treatments. Bacilli reduced total and live spore production of G. orbiculare per mm 2 of lesion and increased beta-1,3-glucanase activity of cucumber apoplastic fluids. Applications of BmJ compared to fungicides for the control of anthracnose in cucumber (var. 'General Lee') and cantaloupe (var. 'Athena') were evaluated in 2004 and 2005 field experiments. BmJ applied seven days before inoculation provided disease reduction in cucumber and cantaloupe statistically equal to the fungicide treatments.Item Functional studies of type II heterodimeric phytochromes and end-modified type I phyAs in arabidopsis(Montana State University - Bozeman, College of Agriculture, 2011) Liu, Peng; Chairperson, Graduate Committee: Robert Sharrock.Phytochromes (phys) are a family of dimeric chromoprotein photoreceptors that modulate plant physiological and developmental processes in response to red (R) and far-red (FR) light. In Arabidopsis thaliana, these fall into two functional groups, type I phyA and type II phyB-E. Previous findings have shown that heterodimerization occurs in type II phytochromes and suggest that diverse dimer forms may have specific functions. The first objective of this study was to characterize the activities of individual phytochrome dimer combinations by developing a novel in vivo protein engineering system. Either obligate homodimers or heterodimers of phytochrome N-terminal regions were produced in phyB mutant plants. With this system, a highly active phyB/D heterodimeric form was shown to rescue the phyB mutant phenotype. Dimers of phyB/achromo-phyB, phyB/C, and phyB/E mediated organ-specific growth in de-etiolation by functioning differentially in cotyledons but not in hypocotyls. Light labile phyA is critical in the plant transition from skotomorphogenic to photomorphogenic growth. To investigate possible in vivo phyA heterodimerization with type II phys and the relationship between phy quaternary structure and signaling mechanisms, transgenic plants were generated that express different myc- tagged N- or C-terminal end fusion phyA proteins in a Landsberg erecta (Ler) phyA mutant or a wild-type background. Co-immunoprecipitation showed that phyA only forms homodimers with itself. Compared with fully active one myc epitope (myc1)-tagged phyAs, six myc epitopes attached to the ends of the N- or C- terminus of phyA impaired phyA-mediated far-red high irradiance (FR-HIR) signaling and also attenuated degradation in the light, indicating that alteration of phyA architecture may damage protein-protein interaction both in phyA downstream signaling and in its protein turnover. Overall, these findings have expanded the structurally complex R/FR sensing systems in plants and have implications for how plant growth and development may be fine-tuned through phy heterodimer-mediated tissue-specific growth or phy-modified activity.Item Characterization of the Arabidopsis compact inflorescence 3 (cif3) mutant and identification of the cif3 gene product as a chloroplast localized putative ATPase(Montana State University - Bozeman, College of Agriculture, 2005) Cameron, Jeffrey Carlyle; Chairperson, Graduate Committee: Robert Sharrock.A new mutant of Arabidopsis, that exhibits very short inflorescence internodes in contrast to the wild-type raceme structure, was isolated from an Agrobacterium tumifaciens T-DNA insertion screen. This plant closely resembles the previously described compact inflorescence (cif1) mutant (Goosey and Sharrock, 2001). The cif1 trait was shown to require altered alleles of two genes; a recessive mutation at the cif1 gene and a naturally occurring unlinked dominant allele, CIF2. Although the phenotypes of cif1 and the new mutant are similar, complementation tests show that they are different genes, and the new mutant is designated cif3. The cif3 mutation is recessive and, unlike the cif1 mutation, does not require the presence of a dominant allele of the CIF2 gene to cause the inflorescence phenotype. Moreover, the cif1 phenotype was previously shown to be restricted to the adult vegetative phase of growth and to strongly influence the morphology of adult rosette leaves. In contrast, cif3 does not show an effect on adult leaves and therefore does not show apparent phase-specific expression. The cif3 mutation is tagged with a T-DNA insertion and the CIF3 gene has been cloned using forward genetics. Northern blot analysis shows expression of a disrupted transcript from the CIF3 gene in the cif3 mutant. A transgenic complementation test was performed and confirms the identity of the CIF3 gene. The CIF3 gene product has been shown to be a chloroplast localized putative ATPase. These studies provide insight into the genetic mechanisms controlling inflorescence development in Arabidopsis and may provide a foundation for understanding inflorescence architecture in agriculturally important crop plants.