title: The use of alpha-amanitin to inhibit in vivo RNA synthesis and germination in wheat embryos.
abstract: Low concentrations (0.10 to 1.0 microgram/ml) of alpha-amanitin inhibit wheat embryo germination. Labeled RNA, synthesized in vivo by embryos imbibed in the presence of [3H]uridine and various concentrations of alpha-amanitin, was analyzed by oligo(dT)-cellulose chromatograhy and by gel electrophoresis (acrylamide and agarose) coupled with fluorography. Low concentrations of alpha-amanitin (0.10 to 1.0 microgram/ml) strongly and selectively inhibited in vivo poly(A) + RNA synthesis in a manner which closely paralleled alpha-amanitin inhibition of purified RNA polymerase II. These results suggest that de novo mRNA transcription is required for germination. Higher concentrations of alpha-amanitin inhibited in vivo 5 S rRNA and tRNA synthesis in a manner which closely paralleled alpha-amanitin inhibition of purified RNA polymerase III. High concentrations of alpha-amanitin also inhibited accumulation of radioactivity into the rRNA precursor as well as into mature 25 S and 18 S rRNAs in a manner which also closely paralleled alpha-amanitin inhibition of RNA polymerase III. The discrepancy of the in vivo inhibitory effect of high alpha-amanitin concentrations on rRNA synthesis versus a lack of effect on purified RNA polymerase I, which presumably transcribes these genes, can be explained if continued transcription of the large rRNA precursor by RNA polymerase I requires ongoing transcription by RNA polymerase III, or if there is degradation (wastage) of rRNA precursor and/or processed products in the absence of transcription by RNA polymerase III.
mesh_terms: D000546:Amanitins / Q000494:pharmacology*; D003513:Cycloheximide / Q000494:pharmacology; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors; D003609:Dactinomycin / Q000494:pharmacology; D008970:Molecular Weight; D018521:Plant Physiological Phenomena; D010944:Plants / Q000187:drug effects; D011061:Poly A / Q000096:biosynthesis; D012313:RNA / Q000096:biosynthesis*; D014158:Transcription, Genetic / Q000187:drug effects*; D014908:Triticum / Q000187:drug effects / Q000502:physiology
chemical_list: D000546:Amanitins; D003609:Dactinomycin; D011061:Poly A; D012313:RNA; D003513:Cycloheximide; D012321:DNA-Directed RNA Polymerases