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Cloning of cDNAs encoding Bombyx homologues of Cdc2 and Cdc2-related kinase from eggs
H Iwasaki1, M Takahashi, T Niimi
1Laboratory of Sericulture and Entomoresources, School of Agricultural Sciences, Nagoya University, Japan.
Abstract:
In diapausing eggs of the silkworm Bombyx mori, embryonic cells are arrested at G2 phase. The ability to undertake cell division is resumed in the course of diapause termination caused by such a treatment as acclimation to 5 degrees C. As an initial trial to investigate the relationship between diapause and embryonic cell cycling, we have cloned and sequenced two Bombyx cDNAs encoding two distinct cdc2-related Ser/Thr protein kinases. One (Bm cdc2) encoded a 37.0 kDa protein which had all of the domains characteristic of other Cdc2 kinase. The other (Bcdrk) encoded a 45.1 kDa protein that was most similar to Drosophila and human cdc2-related protein kinases (Dcdrk protein and PISSRLE kinase). Northern blot analysis was carried out to examine levels of Bm cdc2 and Bcdrk mRNA during embryogenesis of non-diapause eggs. The result demonstrated that the mRNA level of Bm cdc2 appeared to correspond to the activity of nuclear/cellular division in non-diapause eggs, and that the developmental profile in the level of Bcdrk mRNA was somewhat different from that of Bm cdc2 mRNA.
Insights
Silkworm embryonic cells resume division after diapause. Researchers cloned two cdc2-related genes (Bm cdc2 and Bcdrk) and found Bm cdc2 mRNA levels correlate with cell division activity in non-diapause eggs.
Area of Science:
- Molecular Biology
- Developmental Biology
- Cell Cycle Regulation
Background:
- Diapausing silkworm eggs exhibit G2 phase cell cycle arrest.
- Cell division resumes upon diapause termination through treatments like cold acclimation.
- Understanding the molecular mechanisms linking diapause and cell cycle control is crucial.
Purpose of the Study:
- To investigate the relationship between embryonic diapause and cell cycling in Bombyx mori.
- To identify and characterize cdc2-related protein kinases involved in cell cycle regulation during silkworm embryogenesis.
Main Methods:
- Cloning and sequencing of two Bombyx mori cDNAs encoding cdc2-related Ser/Thr protein kinases (Bm cdc2 and Bcdrk).
- Northern blot analysis to examine mRNA expression levels of Bm cdc2 and Bcdrk during non-diapause embryogenesis.
Main Results:
- Bm cdc2 encodes a 37.0 kDa protein with characteristic Cdc2 kinase domains.
- Bcdrk encodes a 45.1 kDa protein homologous to Drosophila and human cdc2-related kinases.
- Bm cdc2 mRNA levels correlate with nuclear/cellular division activity in non-diapause eggs.
- Bcdrk mRNA expression profile differs from Bm cdc2 during development.
Conclusions:
- Bm cdc2 is likely involved in regulating cell division during normal silkworm embryogenesis.
- Bcdrk may play a distinct role in cell cycle regulation, potentially related to diapause or developmental timing.
- Further research is needed to elucidate the specific functions of Bm cdc2 and Bcdrk in relation to diapause and cell cycle control.