Poster: Metabolic Engineering
Abs #
1002: Two distinct phases of cytokinin accumulation and their potential functions in the control of wheat seed development
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Presenter: |
Kaminek, Miroslav , kaminek@ueb.cas.cz |
Authors | Kaminek, Miroslav (A) Dobrev, Petre I. (A) Gaudinova, Alena (A) Motyka, Vaclav (A) Malbeck, Jiri (A) Albrechtova, Jana (B) | | Affiliations: |
(A): Institute of Ezperimental Botany, Academy of Sciences of the Czech Republic
(B): Department of Plant Physiology, Faculty of Science, Charles University
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It is known that the development of cereal seed is accompanied by distinct changes in the concentration of different plant hormones and that a transient peak of cytokinins (CKs) occurs early after pollination. However, the relationship between the concentration changes of a broad spectrum of CKs and endosperm development has not been precisely determined. Using HPLC/MS/MS twenty isoprenoid and one aromatic-side chain CKs were unambiguously identified and quantified in developing wheat seeds. Two different concentration profiles of CKs, differing in their hormonal activities, were found. Massive accumulation of active CKs, trans-zeatin (Z) and its riboside (ZR), and their phosphorylated precursors was associated with endosperm cellularization and the beginning of amyloplast formation. When Z and ZR levels started to decline, transient peaks of Z-O-glucoside and activity of cytokinin oxidase occurred, indicating the conversion of Z to its inactive storage form and corresponding degradative products. Very different concentration dynamics were exhibited by the inactive cis-zeatin riboside (cis-ZR) and its base (cis-Z) which accumulated during seed maturation. Similar changes in concentration profile were exhibited by the aromatic CK, N6-(3-hydroxybenzyl)adenosine. Accumulation of this active CK paralleled that of the CK-binding protein CBF-1, which exhibits high binding activity to aromatic CKs but not to isoprenoid ones. Results indicate that maturating wheat seeds accumulate cytokinins, which are either inactive (cis-Z and cis-ZR) or are inactivated by their binding to CBF-1. These CKs can be activated either by their conversion to active forms or released by degradation of CBF-1 during germination.
Acknowledgement: Supported by the grant No 522/02/0530 of GA CR.
