J-GLOBAL ID:200904002550794138  Research Project code:9910002519 Update date:Jan. 24, 2005

Signal transduction to circadian clock system and regulation of gene expression in response to environmental stimuli

Study period:1997 - 2004
Organization (1):
Investigating Researcher (2):
Research overview:
(1)He detected orthophosphate repressible cyclic phosphodiesterases(cPDase) in the mycelia of Neurospora crassa. The growth of wild type mycelia in low phosphate media derepressed the production of the cPDases leading to the morphogenesis of asexual spore,conidia. eadministration of cAMP or cGMP in the culture media suppressed the morphogenesis of conidia. (2)He isolated mutants in the cPDases,cpd-2 with reduced activities not only in cPDases but also in the adenylate cyclase resulting in the reduced concentrations of cAMP in the mycelia. Similar to the band (bd) sutrain, the cpd-1 and cpd-2 mutants showed clera circadian rhvthm conidiation not only on the solid media but also in the liquid media. the growth of the both mutants on solid media was highly sensitive to light irradition. (3)He first detected circdian oscillation of the concentrations of cAMP and cGMP in the mycelia of N.crassa, and in Lenna paucicostata 381, and the administration of cGMP to the culture media of L.paucicostata381 stimulated the flowering of the plant. In N.crassa the period length of the oscillation of the concentration of cAMP in wild type (bd) and mutants in the conidiation frequency(bd.freq) correlated with the period length of conidiation rhythm. (4)Light irradiation of mycelia grown in darkness showed rapid chage in the concentrations of cAMP and cGMP. He detected several species of cyclic phosphodiesterases being activated by heating and by Mg2+. (5)He developed a hypotheseis that mutual regulation of the concentrations of second messengers including cAMP.cGMP. cytosolic free Ca2+ concentration,diacyl glycerol and inositol trisphosphate may constitute underlying mechanism of circaian rhythm. (6)He developed in vitro systems to analyze the molecular mechanism of signal transduction that used the extract of dark grown mycelia ofbd strain and those of the third internodes of etiolated seedlings of Pisum sativum L. cv. Alaska and the epicotyls of etiolated seedlings of Arabidopsis thalianaL. In case of N. crassa the irradiation of the mycelial extract by blue light increrased the phosphorylation of 15(18)kDa protein,which was identified to be nucleoside diphosphate kinase(NDPkinase) designated as NOK-1. (7)The purified ND Pkinase showed three enzyme activities,g-phosphate transferring activity such as ATP+GDP→ADP+GTP, autophosphorylation activity of Ser and protein kinase activity similar to mitogen activated protein(MAP)kinase,suggesting that NDP Pkinase elicit signal by supplying GTP in the vicinity of GTP-binding proteins,and signal phosphorylating proteins related to the exression of genes similar to MAPkinase. (8)The whole stroy of the results obtained support ollowing hypothesis that light signal changes the cibcebtration of second messengers via GTP-binding proteins, thus changing the phase of circadian rhythm,and that light signal can induce the morphogenesis such as the transition from vegetative mycelia to sexual protoperithecium formation. Similar mechanism may also be functioning in the transition from vegetative state to flowering in plants.
Keywords (6):
arabidopsis thaliana ,  neurospra crassa ,  lemna paucicostate ,  NDPkinase ,  light signal transduction ,  Biological clock
Project name: Signal transduction to cirvadean clock system and regulation of gene expression in response to environmental stimuli Arabidopsis thaliana,Lemna paucicostata and Neurospora Crassa
Project Organization (1):
  • (1152002000)
Researcher representative of the project  (1):
  • HASUNUMA Kohji
Research program: Ordinary Research

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