Nuclear rRNA transcript processing versus internal transcribed spacer secondary structure.

rRNA is one of the few universal features of life, making it uniquely suited to assess phylogenetic relationships. The processing of the initial polycistronic rRNA transcript is also a conserved process, involving numerous cleavage events and the generation of secondary structures. The secondary structure of the internal transcribed spacer (ITS) regions of nuclear rRNA transcripts are well known for a wide variety of eukaryotes and have been used to aid in the alignment of these sequences for phylogenetic comparisons.

Analysis of mammalian rDNA internal transcribed spacers.

Nuclear rDNA Internal Transcribed Spacers, ITS1 and ITS2, are widely used for eukaryote phylogenetic studies from the ordinal level to the species level, and there is even a database for ITS2 sequences. However, ITS regions have been ignored in mammalian phylogenetic studies, and only a few rodent and ape sequences are represented in GenBank. The reasons for this dearth, and the remedies, are described here.

A NEW SPECIES OF VOLVOX SECT. MERRILLOSPHAERA (VOLVOCACEAE, CHLOROPHYCEAE) FROM TEXAS.

Smith (1944) divided the familiar genus Volvox L. into four sections, placing seven species that lacked cytoplasmic bridges between adult cells in the section Merrillosphaera. Herein, we describe a new member of the section Merrillosphaera originating from Texas (USA): Volvox ovalis Pocock ex Nozaki et A.

Is there a molecular key to the level of "biological species" in eukaryotes? A DNA guide.

DNA sequences, powerful for phylogeny, have not yet proven as rewarding for taxonomic categorization purposes. However, further analyses of one locus, the second Internal Transcribed Spacer of the nuclear ribosomal gene cistron, has suggested a high degree of predictability across eukaryotes. Comparison of the secondary structure of ITS2 transcripts reveals its most conserved region, on the 5'-side of helix III.

Secondary structure of the rRNA ITS2 region reveals key evolutionary patterns in acroporid corals.

This study investigates the ribosomal RNA transcript secondary structure in corals as confirmed by compensatory base changes in Isopora/Acropora species. These species are unique versus all other corals in the absence of a eukaryote-wide conserved structural component, the helix III in internal transcriber spacer (ITS) 2, and their variability in the 5.8S-LSU helix basal to ITS2, a helix with pairings identical among all other scleractinian corals.

Identification of the minus-dominance gene ortholog in the mating-type locus of Gonium pectorale.

The evolution of anisogamy/oogamy in the colonial Volvocales might have occurred in an ancestral isogamous colonial organism like Gonium pectorale. The unicellular, close relative Chlamydomonas reinhardtii has a mating-type (MT) locus harboring several mating-type-specific genes, including one involved in mating-type determination and another involved in the function of the tubular mating structure in only one of the two isogametes. In this study, as the first step in identifying the G.

Pan-eukaryote ITS2 homologies revealed by RNA secondary structure.

For evolutionary comparisons, phylogenetics and evaluation of potential interbreeding taxa of a species, various loci have served for animals and plants and protistans. One [second internal transcribed spacer (ITS2) of the nuclear ribosomal DNA] is highly suitable for all. Its sequence is species specific.

Portrait of a species: Chlamydomonas reinhardtii.

Chlamydomonas reinhardtii, the first alga subject to a genome project, has been the object of numerous morphological, physiological, and genetic studies. The organism has two genetically determined mating types (plus and minus) and all stages of the simple life cycle can be evoked in culture. In the nearly 60 years since the first standard laboratory strains were isolated, numerous crosses and exchanges among laboratories have led to some confusion concerning strain genealogy.

The advantages of the ITS2 region of the nuclear rDNA cistron for analysis of phylogenetic relationships of insects: a Drosophila example.

We examined the utility for phylogenetic reconstruction of the second internal transcribed spacer (ITS2), lying between the nuclear 5.8S gene and the gene for large subunit ribosomal RNA, using sequences of Ceratitis, Bactrocera, Musca, and Drosophila. We aligned and analyzed 13 sequences from GenBank and 11 new sequences from diverse species of Drosophila.

Comparison of Eudorina/Pleodorina ITS sequences of isolates from nature with those from experimental hybrids.

Internal transcribed spacer (ITS) regions of nuclear ribosomal repeats were compared among 50 Eudorina and Pleodorina isolates and two Volvox species known to clade with Eudorina species. Of the six major subclades found, four containing Eudorina and Pleodorina illinoisensis isolates, one containing Eudorina and Pleodorina indica, and one containing Volvox gigas and V. powersii, the basal branching order remains uncertain, but the positioning of isolates known to mate was always as nearest neighbors on the terminal branches of the tree.

Exploring the phylogenetic utility of ITS sequences for animals: a test case for abalone (Haliotis).

To evaluate the general utility of sequences of the nuclear rDNA internal transcribed spacer (ITS) regions for phylogenetic analyses of animal species groups and their broader relationships, sequences were obtained for 19 species of the genus Haliotis plus a keyhole limpet and a more distantly related gastropod, the Chilean abalone. Three subclades of Haliotis species appear consistently, each encompassing little variation. They are (A) the North Pacific species, (B) the European species, and (C) the Australia species.