Poster: Metabolic Engineering
Abs #
1001: The Impact of Constitutive Expression of a Phaseolus Zeatin O-glucosyl Transferase Gene on Cytokinin Metabolism in Tobacco
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Presenter: |
Vankova, Radomira , vankova@ueb.cas.cz |
Authors | Vankova, Radomira (A) Dobrev, Petre I. (A) Motyka, Vaclav (A) Malbeck, Jiri (A) Gaudinova, Alena (A) Mok, Machteld C (B) Martin, Ruth (B) Mok, David W S (B) | | Affiliations: |
(A): Institute of Experimental Botany, Academy of Sciences of the Czech Republic
(B): Oregon State University, Department of Horticulture and Center for Gene Research and Biotechnology
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The effect of constitutive expression of a Phaseolus zeatin O-glucosyl transferase gene (ZOG1) on cytokinin (CK) metabolism was examined in transgenic tobacco. trans-[3H]Zeatin (Z) and trans-[3H]zeatin riboside (ZR) were rapidly converted to zeatin O-glucoside in detached leaves of the transformant (line 7). Only trace amounts of these cytokinins were metabolized to [3H]AMP. In contrast, in control plants small amounts of Z and ZR were metabolized to [3H]zeatin 7-glucoside (Z7G) and [3H]dihydrozeatin (DHZ) while the majority was degraded to [3H]adenosine (Ado), [3H]adenine (Ade) and [3H]AMP. The metabolism of [3H]isopentenyladenine (iP) and its riboside did not differ between transgenic and control tissues, and the major products were Ade, Ado, and AMP. Cytokinin oxidase/dehydrogenase (CKX) activity in transgenic tissues (young leaves) was lower (55 % of control), perhaps as a consequence of the reduced level of active CKs through O-glucosylation. Analyses of endogenous CKs in the transgenic tobacco revealed high levels of O-glucosides of Z and cis-zeatin. The levels of unconjugated CKs and 7N-glucosides did not differ significantly between the transgenic and control plants. These results indicate that expression of the transgene increases the reversible, storage form of cytokinins without significantly altering the free cytokinin pool.
Acknowledgement: The research is supported by the Czech Ministry of Education, Youth and Sports , grant Kontakt ME 406 and by U.S. National Science Foundation grant 0086731.
