Molecular evolution of algae and emergence of chloroplasts as deduced from 5S ribosomal RNA sequences.

测定了7种红藻、1种金黄色绿藻、1种硅藻、5种褐藻、裸藻、蓝藻和19种绿色植物的细胞质5S核糖体RNA（rRNA）序列。利用这些序列，已经构建了这些生物的产藻树。红藻门（红藻）、绿色藻（绿色植物的成员）和“有色藻门”（褐藻、硅藻和金黄色的藻类）仅从5S rRNA序列推断出彼此在异源性上有一定的亲缘关系。在真核生物的进化过程中，首先出现红藻，然后依次出现各种真菌、绿色植物（包括绿色藻）和绿藻门。在红藻的进化中，所谓的“原始类群”的红枝藻纲和“更高级类群”的花藻纲在其进化的早期阶段首先彼此分离。该树还表明，各种红藻，如Batrachospermum，Gelidium，Gleiopeltis和Carpopeltis在生殖上彼此相当遥远。因此，红藻是真核生物进化史上分布最广、最古老的分离生物。“绿藻门”包括金黄色藻类、硅藻和褐藻。这三个群体是相互关联的。在“有色藻类”的演化过程中，首先分离出金黄色的绿藻，然后硅藻和褐藻相互分离。尽管褐藻在形态和生活史上存在很大差异，但5SrRNA序列表明褐藻在很短的时间内就已经发生了分化，在叶绿体进化中，绿色植物、裸藻和蓝藻的叶绿体5SrRNA序列与蓝细菌的5SrRNA序列有很高的同源性，表明它们是内共生的。

The cytoplasmic 5S ribosomal RNA (rRNA) sequences from seven red algae, a golden yellow alga, a diatom , five brown algae, Euglena, Cyanophora and 19 green plants have been determined. Using these sequences, a phylogenic tree of these organisms have been constructed.Three types of algae, i.e., Rhodophyta (red algae), green algae (members of green plants), and "Chromophyta" (brown algae, the diatom and the goldenyellow alga) are only remotely related to one anotherphylogenically as deduced from 5S rRNA sequences. Red algae emerged first in the eukaryotic evolution, and thereafter various fungi, green plants including green algae and Chromophyta emerged in this order. In the red algal evolution, the so-called "primitive group" of the class Bangiophyceae and "more advanced group" of the class Florideophyceae separated first from each other in an early stage of their evolution. The tree also indicates that various red algae, such as Batrachospermum, Gelidium, Gleiopeltis and Carpopeltis are phylogenically rather remote from one another. Thus, red algae are very widely and anciently separated organisms in the evolution of eukaryotes."Chromophyta" contains golden-yellow algae, diatoms and brown algae. These three groups are related to one another. During the "Chromophyta" evolution, the golden-yellow alga separated first, and thereafter the diatom and brown algae separated from each other. Although brown algae are very different in their morphology and life cycle, the 5S rRNA sequences clearly indicate that the brown algae were diversified quite recently within a short period.In the chloroplast evolution, 5S rRNA sequences of chloroplasts from green plants, Euglena and Cyanophora species show high homology to Cyanobactrial 5S rRNAs, indicating endosymbiosis of them.