Enzymatic activity, localization, and gene expression of the soybean vegetative storage proteins, VSP Alpha and VSP Beta /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1993.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | The soybean vegetative storage protein genes (vspA and vspB) are regulated in a complex manner developmentally and in response to external stimuli such as wounding and water deficit. VSPα and VSPβ accumulate to almost one-half of the total amount of soluble leaf protein when soybean plants are continually depodded and have been identified as storage proteins because of their abundance and pattern of expression in plant tissues. The purified proteins possess acid phosphatase activity. These enzymes are active over a broad pH range, maintaining greater than 40% of maximal activity from pH 4.0 to 6.5 and having maximal activity from pH 5.0-5.5. These phosphatases can liberate inorganic phosphate from a variety of substrates, but have highest specificity for phosphoenolpyruvate, ATP, ADP, PP, and short-chain polyphosphates. VSPα and VSPβ are localized to the vacuoles of leaf epidermal and paraveinal mesophyll cells. In hypocotyls, these proteins are found in vacuoles of epidermal, cortical, and vascular bundle-associated cells. In addition, they are found to low levels in the cell wall and extracellular spaces. Finally, in water-deficient seedlings there is an altered accumulation, with substantial quantities in the cytoplasm, cell wall, and extracellular spaces. The vsp genes are modulated by methyl jasmonate (MeJA) in combination with soluble carbohydrates, phosphate, nitrogen, and the plant hormone, auxin. A threshold level of soluble sugars is requisite for maximal induction of the vsp genes in suspension cultures, excised leaves, and whole plants. High phosphate levels repress MeJA-induced gene expression, and low levels allow maximal induction. Synthetic (NAA) and naturally occuring (IAA) auxin fully repress MeJA-induced expression at equimolar concentrations with MeJA, and auxin blocks wound-induced expression of these genes. The vspB promoter was analyzed by transforming tobacco with different promoter regions fused to the reporter gene, gus, which encodes β-glucuronidase. In transgenic tobacco, the promoter was induced by MeJA, sucrose, wounding, and combinations thereof. A small domain (50 bp) was identified which could elicit MeJA-response when fused to a minimal promoter. This domain contains a G-box and a C-rich region which may facilitate transcription factor binding. |
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| Item Description: | Vita. "Major subject: Biochemistry." In title, symbols for Greek letters alpha and beta are used. |
| Physical Description: | xiii, 133 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |