The roles of ERK and P38 MAPK signaling cascades on embryonic diapause initiation and termination of the silkworm, Bombyx mori.
To clarify the molecular mechanisms of Bombyx diapause, we focused on mitogen-activated protein kinases (MAPK), which are the major components of signal transduction cascades that regulate cell proliferation, differentiation, and stress responses. In the present study, cloning of Bombyx extracellular signal-related kinase (ERK), MAPK-ERK kinase (MEK), and p38 MAPK cDNA, revealed that their amino acid sequences have close similarity with those of other species. We analyzed the roles of the kinases in diapause initiation and termination by immuno-blotting with anti-phospho-kinase antibodies. Phospho-MEK levels remained consistently high in non-diapausing eggs, then declined after the diapausing stage in diapausing eggs, and began to increase 45 d after transfer to 5 degrees C upon diapause termination. The phospho-ERK and phospho-MEK profiles were similar, suggesting that ERK phosphorylation is regulated by MEK. The phospho-p38 MAPK levels declined 36 h after oviposition in diapausing eggs, and increased at 15-30 d at 5 degrees C in yolk cells, suggesting that p38 MAPK has a role in diapause initiation and termination. Phospho-ERK levels were maintained with diapause-interrupting treatment and declined with diapause-sustaining treatment. ERK phosphorylation is considered to have a role in diapause termination and in the resumption of development.
Fujiwara
Yoshihiro
Y
Faculty of Textile Science and Technology, Department of Applied Biology, Shinshu University, Ueda, Nagano 386-8567, Japan. yoshiro.fujiwara@nifty.com
Shindome
Chiyomi
C
Takeda
Makio
M
Shiomi
Kunihiro
K
D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx / Q000196:embryology* / Q000201:enzymology* / Q000378:metabolism; D003001:Cloning, Molecular; D003080:Cold Temperature; D048049:Extracellular Signal-Regulated MAP Kinases / Q000737:chemistry / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D006851:Hydrochloric Acid; D020935:MAP Kinase Signaling System; D008969:Molecular Sequence Data; D010063:Ovum / Q000201:enzymology / Q000254:growth & development; D010766:Phosphorylation; D017386:Sequence Homology, Amino Acid; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*
D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D006851:Hydrochloric Acid