Hepperle D, Nozaki H, Hohenberger S, Huss V A, Morita E, Krienitz L
Institute of Freshwater Ecology & Inland Fisheries, Department of Limnology of Stratified Lakes, Alte Fischerhütte 2, D-16775 Neuglobsow, Germany.
J Mol Evol. 1998 Oct;47(4):420-30. doi: 10.1007/pl00006399.
Four genera of the Phacotaceae (Phacotus, Pteromonas, Wislouchiella, Dysmorphococcus), a family of loricated green algal flagellates within the Volvocales, were investigated by means of transmission electron microscopy and analysis of the nuclear encoded small-subunit ribosomal RNA (18S rRNA) genes and the plastid-encoded rbcL genes. Additionally, the 18S rDNA of Haematococcus pluvialis and the rbcL sequences of Chlorogonium elongatum, C. euchlorum, Dunaliella parva, Chloromonas serbinowii, Chlamydomonas radiata, and C. tetragama were determined. Analysis of ultrastructural data justified the separation of the Phacotaceae into two groups. Phacotus, Pteromonas, and Wislouchiella generally shared the following characters: egg-shaped protoplasts, a single pyrenoid with planar thylakoid double-lamellae, three-layered lorica, flagellar channels as part of the central lorica layer, mitochondria located in the central cytoplasm, lorica development that occurs in mucilaginous zoosporangia that are to be lysed, and no acid-resistant cell walls. Dysmorphococcus was clearly different in each of the characters mentioned. Direct comparison of sequences of Phacotus lenticularis, Pteromonas sp., Pteromonas protracta, and Wislouchiella planctonica revealed DNA sequence homologies of >/=98. 0% within the 18S gene and 93.9% within the rbcL gene. D. globosus was quite different from these species, with a maximum of 92.9% homology in the 18S rRNA and </=86.6% in the rbcL gene. It showed major similarities to the 18S rDNA of Dunaliella salina, with 95.3%, and to the rbcL sequence of Chlamydomonas tetragama, with 90.3% sequence homology. Additionally, the Phacotaceae sensu stricto exclusively shared 10 (rbcL: 4) characters which were present neither in other Chlamydomonadales nor in Dysmorphococcus globosus. Different phylogenetic analysis methods confirmed the hypothesis that the Phacotaceae are polyphyletic. The Phacotaceae sensu stricto form a stable cluster with affinities to the Dunaliellaes and possibly Haematococcus pluvialis. Dysmorphococcus globosus represented an independent lineage that is possibly related to Chlamydomonas moewusii and C. tetragama.
通过透射电子显微镜以及对核编码的小亚基核糖体RNA（18S rRNA）基因和质体编码的rbcL基因进行分析，对团藻目内具甲鞘的绿色藻类鞭毛虫科（Phacotaceae）的4个属（Phacotus、Pteromonas、Wislouchiella、Dysmorphococcus）进行了研究。此外，还测定了雨生红球藻（Haematococcus pluvialis）的18S rDNA以及细长绿梭藻（Chlorogonium elongatum）、优形绿梭藻（C. euchlorum）、小球藻（Dunaliella parva）、塞尔比诺绿藻（Chloromonas serbinowii）、辐射衣藻（Chlamydomonas radiata）和四角衣藻（C. tetragama）的rbcL序列。超微结构数据分析证明将鞭毛虫科分为两组是合理的。Phacotus、Pteromonas和Wislouchiella通常具有以下共同特征：卵形原生质体、单个具扁平类囊体双层片层的蛋白核、三层甲鞘、作为中央甲鞘层一部分的鞭毛通道、位于中央细胞质中的线粒体、在即将裂解的粘液性游动孢子囊中发生的甲鞘发育，以及无耐酸性细胞壁。Dysmorphococcus在上述每个特征上都明显不同。对透镜状Phacotus、Pteromonas sp.、延长Pteromonas和浮游Wislouchiella的序列进行直接比较，结果显示18S基因内的DNA序列同源性≥98.0%，rbcL基因内的同源性为93.9%。球形D. globosus与这些物种有很大不同，18S rRNA中的同源性最高为92.9%，rbcL基因中的同源性≤86.6%。它与盐生杜氏藻（Dunaliella salina）的18S rDNA有主要相似性，同源性为95.3%，与四角衣藻的rbcL序列有90.3%的序列同源性。此外，狭义的鞭毛虫科仅共有10个（rbcL：4个）特征，这些特征在其他衣藻目以及球形Dysmorphococcus中均不存在。不同的系统发育分析方法证实了鞭毛虫科是多系的这一假说。狭义的鞭毛虫科形成一个稳定的类群，与杜氏藻属以及可能的雨生红球藻有亲缘关系。球形Dysmorphococcus代表一个独立的谱系，可能与莫氏衣藻（Chlamydomonas moewusii）和四角衣藻有关。
