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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Hornwort pyrenoids, carbon-concentrating structures, evolved and were lost at least five times during the last 100 million years
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Hornwort pyrenoids, carbon-concentrating structures, evolved and were lost at least five times during the last 100 million years

机译：在过去的一亿年里，金银花类胡萝卜素（碳富集结构）不断演变并损失了至少五次

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Ribulose-1,5-Biphosphate-carboxylase-oxygenase (RuBisCO) has a crucial role in carbon fixation but a slow catalytic rate, a problem overcome in some plant lineages by physiological and anatomical traits that elevate carbon concentrations around the enzyme. Such carbon-concentrating mechanisms are hypothesized to have evolved during periods of low atmospheric CO_2. Homworts, the sister to vascular plants, have a carbon-concentrating mechanism that relies on pyrenoids, proteinaceous bodies mostly consisting of RuBisCO. We generated a phylogeny based on mitochondrial and plastid sequences for 36% of the approximately 200 hornwort species to infer the history of gains and losses of pyrenoids in this clade; we also used fossils and multiple dating approaches to generate a chronogram for the homworts. The results imply five to six origins and an equal number of subsequent losses of pyrenoids in homworts, with the oldest pyrenoid gained ca. 100 Mya, and most others at <35 Mya. The nonsynchronous appearance of pyrenoid-containing clades, the successful diversification of pyrenoid-lacking clades during periods with low [CO_2], and the maintenance of pyrenoids during episodes of high [CO_2] all argue against the previously proposed relationship between pyrenoid origin and low [CO_2]. The selective advantages, and costs, of hornwort pyrenoids thus must relate to additional factors besides atmospheric CO_2.
机译：核糖-1,5-二磷酸羧化酶加氧酶（RuBisCO）在固碳中起关键作用，但催化速度较慢，在某些植物谱系中，通过提高酶周围碳浓度的生理和解剖学特征克服了这一问题。据推测，这种碳浓缩机制是在大气CO_2较低的时期演变而来的。维他命是维管植物的姊妹，具有一种碳浓缩机制，该机制依赖于类胡萝卜素，蛋白质主体主要由RuBisCO组成。我们基于线粒体和质体序列为约200个金花草物种中的36％生成了系统发育信息，以推断该进化枝中类胡萝卜素的得失历史。我们还使用化石和多种测年方法生成了艾蒿的计时码表。结果表明，在本草中，类胡萝卜素有五到六个起源，随后损失了相同数量的类胡萝卜素，最老的类胡萝卜素获得了约。 100 Mya，而大多数其他用户的<35 Mya。含有类胡萝卜素的进化枝非同步出现，在[CO_2]低的时期成功缺乏类胡萝卜素的进化枝，以及在[CO_2]高的时期维持类胡萝卜素，都与先前提出的类胡萝卜素起源和低[[ CO_2]。因此，除了地球大气中的CO_2以外，金银花类胡萝卜素的选择性优势和成本还必须与其他因素相关。

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