Science2014-06-11 1:30 PM

古老蕨类化石强化王紫萁的"活化石"声誉 Fossilized Nuclei and Chromosomes Reveal 180 Million Years of Genomic Stasis in Royal Ferns

论文摘要 

研究人员发现了一个1亿8000万年前的蕨类化石,它的亚细胞结构得到了纯正的保存,其中包括它的细胞核与染色体,后者非常类似于肉桂蕨类中的分株假紫萁。该古老的化石是在瑞典南部的Korsaröd 发现的,它提示该蕨类植物中的基因组的大小在数亿年中没有改变,它强化了王紫萁(属于分株假紫萁科)的“活化石”声誉。

Benjamin Bomfleur及其同事分析了该蕨类化石并解释了像这么纤细的细胞器能够真的形成化石是多么地罕见;他们提出Korsaröd 标本可能是在其还活着的时候通过热液卤在火山岩中得以保存的。研究人员对该蕨类植物的形成化石的髓部及皮层薄壁细胞的处于间期的细胞核的维度进行了测量,并发现它们与其仍然存活的亲族植物——分株假紫萁——的相应部分十分相似。

基于他们的观察,Bomfleur及他的团队提出,该古老的Korsaröd 蕨在早期侏罗纪时期所含的染色体数及DNA含量基本上与如今的紫箕科蕨相同,使得后者成为演化停滞的最重要例证。


Abstract 

Rapidly permineralized fossils can provide exceptional insights into the evolution of life over geological time. Here, we present an exquisitely preserved, calcified stem of a royal fern (Osmundaceae) from Early Jurassic lahar deposits of Sweden in which authigenic mineral precipitation from hydrothermal brines occurred so rapidly that it preserved cytoplasm, cytosol granules, nuclei, and even chromosomes in various stages of cell division. Morphometric parameters of interphase nuclei match those of extant Osmundaceae, indicating that the genome size of these reputed “living fossils” has remained unchanged over at least 180 million years—a paramount example of evolutionary stasis.

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