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.
Highlights
[’H]uridine and various concentrations of a-amanitin, form of active mRNA, and if de nouo mRNA synthesis is was analyzed by oligo(dT)-cellulosechromatography obligatory for germination at all
The inhibited in vivo poly(A)+ RNA synthesis in a manner enzymes can be distinguished chromatographically, structurwhich closely paralleled a-amanitin inhibitionof purified RNA polymerase Lt.These results suggest that de novo mF4NA transcription is required for germination
Plant RNA polymerases have similar a-amanitin increpancy of the in vivo inhibitory effecot f high a-aman- hibition properties, chromatographic properties, and subunit itin concentrations onrRNA synthesis versus a lackof structures to the cognate mammalian enzymes [19].The role effectonpurifiedRNA polymeraseI, which presumably of RNA polymerase I in rRNA synthesis has been demontranscribes these genes, can be explained i f continued strated in higher plants by analysis of nascent RNA elongated transcription of thelarge rRNAprecursorbyRNA polymerase I requires ongoing transcriptionbyRNA
Summary
From the Departmentof Botany, University of Minnesota, St. Paul, Minnesota 55108. The inhibited in vivo poly(A)+ RNA synthesis in a manner enzymes can be distinguished chromatographically, structurwhich closely paralleled a-amanitin inhibitionof purified RNA polymerase Lt.These results suggest that de novo mF4NA transcription is required for germination. Plant RNA polymerases have similar a-amanitin increpancy of the in vivo inhibitory effecot f high a-aman- hibition properties, chromatographic properties, and subunit itin concentrations onrRNA synthesis versus a lackof structures to the cognate mammalian enzymes [19].The role effectonpurifiedRNA polymeraseI, which presumably of RNA polymerase I in rRNA synthesis has been demontranscribes these genes, can be explained i f continued strated in higher plants by analysis of nascent RNA elongated transcription of thelarge rRNAprecursorbyRNA polymerase I requires ongoing transcriptionbyRNA polymerase III,or if thereis degradation (wastage)of rRNA precursor and/or processed productsin the absence of transcriptionby RNA polymerase III. The transcription products of plant RNA polymerase 111 have not yet been demonstrated
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