生物谷报道：由孟德尔首次观察到的遗传原理是足够清楚的。遗传信息在生物体的每个细胞中都有的染色体所携带的DNA中从父辈传给子辈，在如线粒体和叶绿体等细胞器中的辅助基因组中也进行着这样的遗传信息传递，只是程度小一些。但对拟南芥（Arabidopsis thaliana）中发生回复突变的hothead基因突变体所做的分析表明，这些植物能遗传在父辈染色体中没有、但与祖父或更远祖先的染色体中相同的信息。这可能涉及从一个RNA存放处传递来的祖先DNA在模板引导下的恢复，这种RNA存放处就像一个存放旧网页的浏览器存放处一样。研究这种形式的遗传是否普遍存在将会很有趣。本期封面所示为一株有hothead突变体的花（扫描电子显微图片由M. A. Webb提供）。
该文发表在 Nature 434, 505 - 509 (24 March 2005); doi:10.1038/nature03380
详细参加如下：
Genome-wide non-mendelian inheritance of extra-genomic information in Arabidopsis
SUSAN J. LOLLE*, JENNIFER L. VICTOR, JESSICA M. YOUNG & ROBERT E. PRUITT*
Department of Botany and Plant Pathology, Purdue University, 915 W. State Street, West Lafayette, Indiana 47907-2054, USA
* These authors contributed equally to this work
Correspondence and requests for materials should be addressed to R.E.P. (pruittr@purdue.edu).
A fundamental tenet of classical mendelian genetics is that allelic information is stably inherited from one generation to the next, resulting in predictable segregation patterns of differing alleles. Although several exceptions to this principle are known, all represent specialized cases that are mechanistically restricted to either a limited set of specific genes (for example mating type conversion in yeast) or specific types of alleles (for example alleles containing transposons or repeated sequences). Here we show that Arabidopsis plants homozygous for recessive mutant alleles of the organ fusion gene HOTHEAD (HTH) can inherit allele-specific DNA sequence information that was not present in the chromosomal genome of their parents but was present in previous generations. This previously undescribed process is shown to occur at all DNA sequence polymorphisms examined and therefore seems to be a general mechanism for extra-genomic inheritance of DNA sequence information. We postulate that these genetic restoration events are the result of a template-directed process that makes use of an ancestral RNA-sequence cache.
