Author
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HUYNH, LE NGUYEN - OHIO STATE UNIVERSITY |
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Submitted to: Ohio State University Thesis
Publication Type: Other Publication Acceptance Date: 2/28/2003 Publication Date: 3/21/2003 Citation: HUYNH, L. INDUCTION OF IPT GENE IN SAG12:IPT TRANSGENIC ARABIDOPSIS PLANTS IN RESPONSE TO FLOODING STRESS. MASTERS THESIS. 2003. THE OHIO STATE UNIVERSITY. 65 P. Interpretive Summary: Technical Abstract: Flooding is one of the most serious environmental stresses affecting plant growth and productivity. Flooding also causes significant losses of agricultural productivity and growers' income each year. Hormones, such as cytokinin, control growth and development and regulate aging of plants. Flooding interferes with the production of these hormones, causing premature aging and leading to slow growth, low yield and sometimes death of the plants. The ipt gene encodes isopentenyl transferase, the rate limiting enzyme in cytokinin biosynthesis. Transgenic Arabidopsis plants expressing ipt under the control of the senescence-associated SAG12 promoter show normal growth and development. This study identified and cataloged differential impacts of waterlogging and submergence stresses on the wild type and SAG12:ipt transgenic plants at the phenotypic and gene expression levels. The phenotypic responses to stress that were quantified are plant biomass, sugar and chlorophyll contents. The temporal patterns of ipt expression, cytokinin and abscisic acid (ABA) accumulation were determined during a 0 to 5 day waterlogging or submergence period. The results showed that 5 days of waterlogging did not affect the biomass of SAG12:ipt plants but significantly reduced growth of wild type (Wt) plants. The enhanced waterlogging tolerance of the SAG12:ipt plants was accompanied by increased cytokinin and sucrose accumulation. The pattern of ABA accumulation was similar to the pattern of cytokinin accumulation. Total submergence was much more detrimental to plant growth than waterlogging, and no difference between wild type and SAG12:ipt plants was detected. Enhanced expression of ipt was not accompanied by increased cytokinin accumulation in plants subjected to submergence. This observation suggests that translation is impacted by submergence, or the activity of the translated product is inhibited. After flooding, the SAG12:ipt transgenic plants showed their ability to recover faster than Wt by gaining greater biomass yield and accumulating more sucrose and cytokinin, following either waterlogging or submergence conditions. The ipt system provides a convenient model to study the interactions between cytokinin biosynthesis and abiotic stress tolerance in plants. |
