Date of Award
3-17-2020
Document Type
Dissertation
Degree Name
Molecular Biosciences, Ph.D.
First Advisor
Dr. Argelia Lorence
Committee Members
Dr. Fabricio Medina-Bolivar; Dr. Fiona Goggin; Dr. Maureen Dolan; Dr. Travis Marsico
Call Number
LD 251 .A566d 2019 N47
Abstract
Myo-inositol oxygenase (MIOX) is the first enzyme in the inositol route to ascorbate (L-ascorbic acid, AsA). Over-expression of MIOX in plants leads to elevated AsA content and enhanced growth rate, biomass accumulation, and tolerance to abiotic stresses. In this work, a combination of transcriptomics, phenomics, cell biology, LC-MS/MS, and physiological measurements were used to gain a better understanding of the molecular mechanisms underlying the phenotype of the MIOX lines. Transcriptomic analysis revealed increased expression of genes involved in auxin synthesis, auxin conjugation, hydrolysis, transport, and metabolism, supported by elevated auxin levels both in vitro and in vivo, and confirmed by assays demonstrating their effect on epidermal cell elongation in the MIOX over-expressers. Additionally, we detected up-regulation of transcripts involved in photosynthesis, increased photosystem II efficiency, and proton motive force. We found enhanced expression of amylase leading to higher intracellular glucose levels. Multiple gene families conferring plants tolerance/expressed in response to salt, cold, and heat stresses were also elevated in the MIOXline. These results indicate that elevated levels of auxin and glucose and enhanced photosynthetic efficiency in combination with up-regulation of abiotic stresses response genes underly the higher growth rate and abiotic stresses tolerance phenotype of the MIOX line. AVP1-1 (H+-pyrophosphatase) and MIOX are proteins that when over-expressed individually lead to plants with enhanced growth and abiotic stress tolerance. In this work, MIOX and AVP1-1 reciprocal crosses were developed, and phenomic approaches were used to investigate the possible synergy between these genes. Under normal and abiotic stress conditions the crosses had higher foliar AsA content. The crosses displayed enhanced growth rate and biomass accumulation compared to parent lines and wild type grown under water limitation. This phenotype may be explained by enhanced photosystem II efficiency, increased linear electron flow, and higher relative chlorophyll content. Additionally, the crosses preserved more water compared to controls when subjected to salt stress. The crosses also produced more seeds compared to controls grown under salt and water limitation stresses. Overall, these results indicate, combinatorial effect of the MIOX4 and AVP1 overexpression may be advantageous for crop improvement as this provides additional stress tolerance and enhanced seed yield compared to the use of individual traits.
Rights Management
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Nepal, Nirman, "Transcriptomics And Phenomics Analysis of High Ascorbate Arabidopsis Myo-Inositol Oxygenase Overexpressers" (2020). Student Theses and Dissertations. 432.
https://arch.astate.edu/all-etd/432
