HERITABLE REPRESSION DUE TO PARAMUTATION IN MAIZE
HERITABLE REPRESSION DUE TO PARAMUTATION IN MAIZE
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DOI：
10.1126/science.162.3856.925
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发表时间：
1968-01-01
期刊：
影响因子：
56.9
通讯作者：
COE, EH
中科院分区：
文献类型：
--
作者：
COE, EH
在brink、Styles和Axtell(1)对玉米R位点参数的深入分析和解释中，我简要地考虑了我提出的关于B位点现象的信息。尽管B的数据清楚地表明，该系统和其他系统中的参数化很可能被解释为减数分裂和末期现象，但Brink、Styles和Axtell的解释是，所有参数化都是体细胞的（或者更确切地说，是减数分裂前的），并且B的数据没有对这一点提出质疑。他们的结论是，在theR位点的参数化不可能涉及粒子在al-水平之间的转移，这也需要相关的评论。只有当这些参数化的机械特征被定义时，参数化系统是否涉及典型的或独特的基因调控机制，以及参数化的生物学意义是个体发生的还是系统发生的，才会变得清晰。b基因座的参数化发生在个体发育后期。这一结论基于明确的证据，部分是表型的，部分是发育的(2)。Brink、Styles和Axtell从几个植物物种中引用的例子支持相反的结论，这些例子都依赖于传统观点，即体细胞分割表明在有丝分裂时发生了准突变。正如在其他地方(2)所讨论的那样，导致扇区的不同有丝分裂可能在参数化的可能性上不同，而不是在参数化事件本身。McClintock(3)在抑制控制系统的“预设”现象中也发现了类似的延迟时间，在这种现象中，基因在发育的一个阶段被编程，随后以模式一致的方式发挥作用，甚至迟至下一代。B数据表明，整个或大部分生命周期可以在准突变杂合子和准突变杂合子的形成之间进行干预
In the penetrating analysis and inter-pretation of paramutation at the R locus in maize byBrink, Styles, and Axtell (1), information that I have presented on the phenomenon at the B locus is briefly considered. Although the B data clearly show that paramutation in this system and others might well be interpreted asa meiotic and terminal phe-nomenon, the interpretation of Brink, Styles, and Axtell is that all paramutation is somatic (or, rather, premeiotic), and that the data for B do not raise doubt on this point. Related comments are needed also on theirconclusion that paramutation at theR locus cannot in-volve transfer of particles between al-leles. Only when these mechanical features of paramutation are defined will it become clear whether paramutation systems involve typical or unique mecha-nisms of gene regulation, and whether the biological significance of paramutation is ontogenetic or phylogenetic. Paramutation at theB locus occurs late in ontogeny. This conclusion rests on clear evidence, partly phenotypic and partly developmental (2). Examples cited by Brink, Styles, and Axtell from several plant species in support of an opposite conclusion all depend on the conventional view that somatic sectoring demonstrates the occurrence of para-mutation in the mitosis at which the sector was delimited. As discussed elsewhere (2), differential mitoses that result in sectors may be differential in the po-tential for paramutation, rather than in the paramutation event itself. Similar delayed timing in repression-control systems has been found by McClintock (3) in the" presetting" phenomenon, in which a gene is programed at one stage of development to function subsequently in patterned concert, even as late as in the next generation. The B data show that all or most of a life cycle can intervene between the formation of the para-mutational heterozygote and the paramu-