Strelkov L A, Gauze L N, Kafiani K A
Mol Biol (Mosk). 1976 Jan-Feb;10(1):99-107.
It has been shown previously that the production of "mature" (27S and 18S) ribosomal RNA's (rRNA) at late stages of embryonic development of the loach (Misgurnus fossilis) does not depend on the degree of ploidy, the haploid (1n) embryos making, per cell, as much rRNA as do the diploid (2n) ones. In order to investigate the mechanims of the compensation of rRNA production in 1n embryos, incorporation of labelled nucleosides in different RNA fractions was compared in two genetical variants. The kinetic and sedimentation analysis showed that in 1n cells a compensatory increase in the production of 36S precursor of rRNA (pre-rRNA) takes place. Chase experiments showed that the rate of the processing and decay of the pre-rRNA was similar in the two genetic forms. Saturation hybridization of labelled, purified 27S rRNA with DNA isolated from the nuclei of 1n and 2n embryos failed to reveal any significant differential increase (amplification) in the proportion of ribosomal cistrons (rDNA) in the haploid genome. It is concluded that the compensation of the production of rRNA in the haploid embryos is accounted for by a greater rate of transcription of the totality of the ribosomal cistrons per single chromosome set.
先前的研究表明，泥鳅（Misgurnus fossilis）胚胎发育后期“成熟”（27S和18S）核糖体RNA（rRNA）的产生不依赖于倍性程度，单倍体（1n）胚胎每个细胞产生的rRNA与二倍体（2n）胚胎一样多。为了研究单倍体胚胎中rRNA产生补偿的机制，在两个遗传变体中比较了标记核苷掺入不同RNA组分的情况。动力学和沉降分析表明，在单倍体细胞中，rRNA的36S前体（前体rRNA）产生有补偿性增加。追踪实验表明，两种遗传形式的前体rRNA加工和衰变速率相似。用从单倍体和二倍体胚胎细胞核中分离的DNA与标记的纯化27S rRNA进行饱和杂交，未能揭示单倍体基因组中核糖体顺反子（rDNA）比例有任何显著的差异增加（扩增）。得出的结论是，单倍体胚胎中rRNA产生的补偿是由于每个单染色体组中核糖体顺反子整体转录速率更高。
