Poster: Cell Cycle & Cytokinesis
Abs #
1096: Characterization of cyclin dependent kinase inhibitor with respect to endoreduplication during maize endosperm development
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Presenter: |
Coelho, Cintia M, coelho@ag.arizona.edu |
Authors | Coelho, Cintia M (A) Sun, Yuejin (B) Dilkes, Bryan P (A) Dante, Ricanrdo A (A) Gordom-Kamm, William (B) Larkins, Brian A (A) | | Affiliations: |
(A): University of Arizona
(B): Pioneer Hi-Bred Internatinal, Inc.
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The mechanisms by which an endoreduplication cell cycle is created have been well documented in several types od specialized animal cells, but little is known regarding how this occurs in plants, let alone the key cell cycle regulatory proteins involved. Recent studies in both animal and plant systems suggest that endoreduplication requires a mechanism that stalls cell cycle progression, followed by loss of M-phase CDK activity and oscillations in the activity of S-phase CDKs. Our studies with maize endosperm showed the accumulation of a CDK inhibitor coincident with the onset of endoreduplication, but the nature of this inhibitor is unknown, nor it is clear wether it affects the M- or S-phase CDK. To address this questions, we identified three putative CDK inhibitor (CKI) clones in the Pioneer EST database. These clones share four regions of identity with Arabdopsis CKI's. They have a commom C-terminal region that is related to the CDK-2 binding domain of mammalian Cip/Kip family members, such as p27. RT-PCR analysis showed that mRNAs corresponding to two of these, CKI-b and -c, are present in endosperm tissue, and immunoblotting with CKI-c antiserum showed this protein accumulates during the period of endoreduplication. M- and S-phase CDKs were immunoprecipitated by incubating maize endosperm extracts with antibodies against cyclinDc and cyclinB1;3, respectively. This assay showed the CKI-c inhibits the cyclinDc/CDK, but not cyclinB1;3/CDK activity. Current experiments are directed at determining if CKI-c corresponds to the CDK inhibitory activity that accumulates during the onset of endoreduplication.
