No abstract

Sequence comparisons of small subunit ribosomal RNA coding regions from 12 chlorophylls a + c-containing algae were used to infer phylogenetic relationships within the Chromophytao Three chromophyte lines of descent, delineated by the Bacillariophyceae, the Phaeophyceael Xanthophyceae, and the Chrysophyceae/Eustigmatophyceae/Synurophyceae are members of a complex evolutionary assemblage, which also includes representatives of the Oomycota ("lower" fungi). Maximum parsimony and distance matrix methods demonstrate a common evolutionary history for these lineages but their relative branching order could not be determined. Other algal species with chlorophylls a + c, including dinoflagellates and prymnesiophytes, are not members of this complex assemblage. Dinoflagellates are specifically related to apicomplexans and ciliates, and the prymnesiophyte, Emiliania huxleyi, represents an independent photosynthetic lineage that separated from other eukaryotes during the nearly simultaneous divergence of plants, animals, fungi, and a number of other protist lineages. The small subunit rRNA phylogenies of chromophytes/oomycetes were compared to those derived from comparisons of ultrastructural characters. Only tubular, tripartite mastigonemes (flagellar hairs) characterized all studied taxa of chromophytes/oomycetes as a monophyletic assemblage.

Embryo lethality patterns induced by an avian influenza virus isolate (A/Tk/Ws/68/H5N9) suggested that it contained more than one genetic form. Two different virus populations were recovered from the isolate by plaque isolation and limit-dilution cloning and were characterized with respect to their biological and molecular properties. They were very closely related but exhibited strikingly different mean death times (MDT) in 10-day-old chick embryos. One was rapidly embryo lethal (REL), while the other was slowly embryo lethal (SEL). The REL isolate demonstrated a small but measurable mortality rate in 4-week-old chicks, as did the parental isolate. The SEL isolate, however, was nonlethal to 4-week-old chicks. The embryo MDT induced by the parental isolate revealed a biphasic death pattern reflecting expression of both REL and SEL populations. Mixing experiments, using different amounts of the two cloned populations, demonstrated that expression of their unique phenotypic property (either REL or SEL) was competitive. The number of early or late embryo deaths was directly related to the input levels of each respective virus. The only molecular difference thus far detected between the two populations is in the nonstructural (NS) gene, with the REL clone possessing a faster migrating electrophoretic form of that RNA than the SEL clone. Both forms of the NS gene were present in the original parental isolate. This study thus demonstrates the competitive coexistence of two closely related virus populations within a single natural isolate.

Breeding psittaciform birds (psittacines) from three geographically separated aviaries experiencing fledgling mortality were monitored during 1983 and 1984 for specific serum antibody to budgerigar fledgling disease virus (BFDV) using a fluorescent-antibody virus-neutralization test. Neither the time nor the extent of exposure to the virus was known. Serological titers were positive in 45% of birds sampled from Aviary 1, 25% from Aviary 2, and 11% from Aviary 3. Several species of psittacine birds within each aviary were serologically positive for BFDV. The results indicated that a papovavirus similar to BFDV appears to infect a wide range of captive adult psittacine birds. Macaws (Ara sp. and Anodorhynchus sp.) were evaluated for distribution of infection. Each species within these two genera showed positive serological titers to BFDV. Three groups of birds showed a decrease in serum antibody titer to BFDV at 1 and 2.5 months after the first sampling. Positive titers decreased from 66 to 20% for one group and from 60 to 50% for a second group in 1 month, and they decreased from 42 to 17% for a third group in 2.5 months.

Abstract. -Sequence comparisons of small subunit ribosomal RNA coding regions from 12 chlorophylls a + c-containing algae were used to infer phylogenetic relationships within the Chromophytao Three chromophyte lines of descent, delineated by the Bacillariophyceae, the Phaeophyceael Xanthophyceae, and the Chrysophyceae/Eustigmatophyceae/Synurophyceae are members of a complex evolutionary assemblage, which also includes representatives of the Oomycota ("lower" fungi). Maximum parsimony and distance matrix methods demonstrate a common evolutionary history for these lineages but their relative branching order could not be determined. Other algal species with chlorophylls a + c, including dinoflagellates and prymnesiophytes, are not members of this complex assemblage. Dinoflagellates are specifically related to apicomplexans and ciliates, and the prymnesiophyte, Emiliania huxleyi, represents an independent photosynthetic lineage that separated from other eukaryotes during the nearly simultaneous divergence of plants, animals, fungi, and a number of other protist lineages. The small subunit rRNA phylogenies of chromophytes/oomycetes were compared to those derived from comparisons of ultrastructural characters. Only tubular, tripartite mastigonemes (flagellar hairs) characterized all studied taxa of chromophytes/oomycetes as a monophyletic assemblage.Key words.-Chromophyte algae, phylogeny, rRNA.Received August 5, 1991. Accepted February 26, 1992 Eukaryotic algae are nonvascular plants that have been traditionally classified according to plastic characteristics such as accessory pigments and thylakoid structure (Dodge, 1974;Taylor, 1976). The major taxonomic groups include red algae (Rhodophyta), green algae (Chlorophyta), and brown plus golden-brown algae (Chromophyta). Ultrastructure and molecular sequence similiarities demonstrate that chlorophylls a + b containing green algae (except for photosynthetic euglenoids) share a unique evolutionary history with multicellular green plants. In contrast the Rhodophyta and Chromophyta are members of the Protista which is represented by paraphyletic lines of descent that cannot be definitively placed in a phylogenetic context using traditional methods of comparative morphology, physiology, or biochemistry. This is especially true for chromophytes since they can no longer be considered as a I Address for reprint requests. monophyletic group on the basis of plastid features (Gunderson et al., 1987;Bhattacharya and Druehl, 1988;Williams, 1991;Andersen, 1991). For example, dinoflagellates have plastids containing chlorophylls a + c and were traditionally placed within the Chromophyta (Christensen, 1980(Christensen, , 1989South and Whittick, 1987;Dodge, 1989) but molecular studies show their relationship with apicomplexans and ciliated protozoa (Gajadhar et al., 1991).The Chromophyta are traditionally defined by 10 major classes which can be differentiated on the basis ofultrastructure and plastid characteristics (Green et al., 1989). The classes include the Bacillariophyceae, Chry...