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Multiple cyclin-dependent kinase complexes and phosphatases control G2/M progression in alfalfa cells
T Mészáros1, P Miskolczi, F Ayaydin
1Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, Szeged.
Plant Molecular Biology
|November 23, 2000
Summary
Plant cell division is complex, involving multiple cyclin-dependent kinases (CDKs) and cyclins that regulate the G2/M transition. Research highlights Cdc2Ms F kinase
Area of Science:
- Molecular Biology
- Plant Cell Biology
- Biochemistry
Background:
- Reversible protein phosphorylation by kinases and phosphatases is crucial for eukaryotic cell cycle control.
- Cyclin-dependent kinases (CDKs) and cyclins are increasingly recognized for their roles in plant cell cycle regulation.
- Alfalfa exhibits complex CDK and cyclin interactions, suggesting intricate regulatory pathways for G2/M transition.
Purpose of the Study:
- To investigate the roles of specific cdc2-related genes (cdc2Ms A, B, D, F) and D-type cyclins in alfalfa G2/M phase progression.
- To explore the involvement of phosphatases in regulating plant cell division.
- To elucidate the complex regulatory mechanisms governing the G2/M transition in flowering plants.
Main Methods:
- Expression analysis of cdc2-related genes (cdc2Ms A, B, D, F) in G2 and M phase cells.
- Phosphorylation assays to identify active kinase complexes.
- Yeast two-hybrid analyses to study cyclin-CDK interactions.
- Immunolocalization of Cdc2Ms F kinase.
- Inhibitor studies using okadaic acid and endothall to assess phosphatase activity.
- Biochemical assays to measure kinase activity.
Main Results:
- Multiple cdc2-related genes (cdc2Ms A, B, D, F) are expressed in G2/M cells, forming successively active kinase complexes.
- Differential interactions were observed between D-type cyclins and Cdc2Ms kinases.
- Cdc2Ms F kinase localized to key mitotic structures (PPB, spindle, phragmoplast), indicating a pivotal role.
- Tyrosine phosphorylation of Cdc2Ms A and enhanced kinase activity with Drosophila Cdc25 suggest phosphatase involvement.
- Inhibitor studies indicated a role for serine/threonine phosphatases, with endothall increasing G2-phase kinase activity.
Conclusions:
- The G2/M transition in flowering plants is regulated by complex, multicomponent pathways involving various CDKs and cyclins.
- Cdc2Ms F kinase plays a significant role in plant mitosis.
- Phosphatase activity is implicated in regulating plant cell division, though further research is needed.
- Biochemical and cytological data collectively emphasize the intricate nature of G2/M regulation in plants.