High cAMP in spores of Dictyostelium discoideum: association with spore dormancy and inhibition of germination.
Microbiology (Reading)
; 145 ( Pt 8): 1883-1890, 1999 Aug.
Article
em En
| MEDLINE
| ID: mdl-10463154
ABSTRACT
Signalling mechanisms involving cAMP have a well-documented role in the coordination of multicellular development and differentiation leading to spore formation in the social amoeba, Dictyostelium discoideum. The involvement of cAMP in the poorly understood developmental stages of spore dormancy and germination have been investigated in this study. Dormant spores contained up to 11-fold more cAMP than nascent amoebae. The spore cAMP levels were not constant, but typically underwent a surge at 14-18 d when spores acquired the ability to germinate spontaneously. The high cAMP levels decreased only during successful spore germination, i.e. emergence of nascent amoebae. The temporal pattern of cAMP decrease was complex and unique to the method of spore activation, supporting our hypothesis that exogenously (e.g. heat) activated and autoactivated spores germinate by different mechanisms. During heat-induced activation, transcription of acg (a gene encoding adenylyl cyclase associated with germination) correlated well with spore cAMP content. Young wild-type spores, incapable of spontaneous germination, maintained a uniformly high cAMP level, and spore cAMP levels also remained high if germination was inhibited. When activated spores were deactivated by applying increased osmotic pressure, cAMP concentrations rose and ultimately levelled off at the high levels typical of dormant spores. The correlation between high cAMP and failure to germinate was also evident when autoactivation was inhibited by the cAMP analogue, 8-bromo-cAMP. Also, spores from a strain (HTY217) with unrestrained protein kinase A activity were incapable of spontaneous germination. Overall, our experiments provide evidence for continued cAMP signalling in spores up to 18 d after sporulation and for linkages between elevated cAMP, spore deactivation and inhibition of spontaneous germination.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
AMP Cíclico
/
Dictyostelium
Tipo de estudo:
Risk_factors_studies
Limite:
Animals
Idioma:
En
Revista:
Microbiology (Reading)
Ano de publicação:
1999
Tipo de documento:
Article