When etiolated Euglena gracilis was treated with 10 mM 5-azacytidine (5-azaC), an inhibitor of DNA methylation, stimulation of plastidogenesis in both dark and light conditions was observed. The phenomenon occurred in 10-15% of the cells possibly due to the asynchronicity of the cultures. The main features of this sub-population, as evaluated by electron and fluorescence microscopy, were the following: 1. the presence in darkness of differentiating proplastids that were red fluorescent under UV, positive to TCNBT cytochemical reaction (specific for PSII) and negative to DAB (specific for PSI); 2. the acceleration of proplastid differentiation during the first 20-30 h of illumination; 3. the occurrence in both culture conditions of concentric lamellar bodies (LBS). These structures were considered to be proplastids blocked in the first step of evolution, since they emitted a red fluorescence, were contained within compartments limited by a triple-layered envelope, were reactive to TCNBT in darkness and to both TCNBT and DAB in light conditions. Even if the action mechanism of 5-azaC on plastidogenesis in Euglena remains to be defined, the induced stimulatory effect on plastid differentiation pointed to a relationship between DNA methylation and plastid development. Furthermore, the presence of LBS opens the possibility of studying early aspects of plastid development in Euglena.
Stimulation of plastidogenesis induced by 5-azacytidine in Euglena gracilis klebs
PANCALDI, Simonetta;BONORA, Angelo;MUZZOLI, Mariavittoria;FASULO, Maria Palmira
1997
Abstract
When etiolated Euglena gracilis was treated with 10 mM 5-azacytidine (5-azaC), an inhibitor of DNA methylation, stimulation of plastidogenesis in both dark and light conditions was observed. The phenomenon occurred in 10-15% of the cells possibly due to the asynchronicity of the cultures. The main features of this sub-population, as evaluated by electron and fluorescence microscopy, were the following: 1. the presence in darkness of differentiating proplastids that were red fluorescent under UV, positive to TCNBT cytochemical reaction (specific for PSII) and negative to DAB (specific for PSI); 2. the acceleration of proplastid differentiation during the first 20-30 h of illumination; 3. the occurrence in both culture conditions of concentric lamellar bodies (LBS). These structures were considered to be proplastids blocked in the first step of evolution, since they emitted a red fluorescence, were contained within compartments limited by a triple-layered envelope, were reactive to TCNBT in darkness and to both TCNBT and DAB in light conditions. Even if the action mechanism of 5-azaC on plastidogenesis in Euglena remains to be defined, the induced stimulatory effect on plastid differentiation pointed to a relationship between DNA methylation and plastid development. Furthermore, the presence of LBS opens the possibility of studying early aspects of plastid development in Euglena.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
