应用荧光原位杂交技术首次确定了日本小檗(B erberis thunberg ii DC)、车前(P lantag o m ajor L.)、野芹菜(S an icu la lam ellig era H ance)、荔枝(L itch i ch inensis Sonn.)、槭树(A cer buerg erianum M iq.)、天目琼花(V iburnum sarg entii K oehne.)、丹参(S a lv ia m iltorrh iza Bunge.)、榆树(U lm us pum ila L.)中45S rDNA在中期染色体上的位置.根据rDNA的位点数和位置的变化,分为四种类型:①在日本小檗、车前和野芹菜中,荧光信号正好位于随体染色体的次缢痕或端部;②荔枝和槭树,分别有1对和3对染色体具随体,但荧光原位杂交却检测到3对和5对染色体上具有杂交信号;③天目琼花,具有4对随体染色体,但仅在其中一对随体上显示了杂交信号;④在丹参和榆树中,有的杂交信号位于着丝粒部位或长臂的末端,杂交信号的数目成奇数.黄瓜(Cucum issa tivus L.)的染色体45S rDNA信号正好位于6条染色体的着丝粒部位,这与D a l-Hoe和Hosh i等人的结果是一致的.上述结果表明:45S rDNA可以作为染色体的一个识别指标,对识别染色体的个体性具有一定的参考价值.另外还对45S rDNA位点分布的多态性进行了讨论.
Large scale cDNA sequencing and genome tiling array studies have shown that around 50% of genomic DNA in humans is transcribed, of which 2% is translated into proteins and the remaining 98% is non-coding RNAs (ncRNAs). There is mounting evidence that these ncRNAs play critical roles in regulating DNA structure, RNA expression, protein translation and protein functions through multiple genetic mechanisms, and thus affect normal development of organisms at all levels. Today, we know very little about the regulatory mechanisms and functions of these ncRNAs, which is clearly essential knowledge for understanding the secret of life. To promote this emerging research subject of critical importance, in this paper we review (1) ncRNAs' past and present, (2) regulatory mechanisms and their functions, (3) experimental strategies for identifying novel ncRNAs, (4) experimental strategies for investigating their functions, and (5) methodologies and examples of the application of ncRNAs.
QI Liwang, LI Xinmin, ZHANG Shougong & AN Daochang Laboratory of Cell Biology, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China
