Radiation and speciation of spider monkeys,genus Ateles,from the cytogenetic viewpoint

The chromosomes of 22 animals of four subspecies of the genus Ateles (A. paniscus paniscus, A. p. chamek, A. belzebuth hybridus, and A. b. marginatus) were compared using G/C banding and NOR (nucleolar organizer region) staining methods. The cytogenetic data of Ateles in the literature were also used to clarify the phylogenetic relationships of the species and subspecies and to infer the routes of radiation and speciation of these taxa. Chromosomes 6 and 7 that showed more informative geographic variation and the apomorphic form 4/12, exclusively in A. p. paniscus, are the keys for understanding the evolution, radiation, and specification of the Ateles taxa. The ancestral populations of the genus originated in the southwestern Amazon Basin (the occurrence area of A. paniscus chamek) and spread in the Amazon Basin and westward, crossing the Andes and colonizing Central America and northwesternmost regions of South America. The evolutionary history of the northern South American taxa is interpreted using the model of biogeographical evolution postulated by Haffer [Science 185:131–137, 1969]. Ateles paniscus paniscus is the genetically most differentiated form and probably derives from A. belzebuth hybridus. Based on the karyotype differences, the populations of Ateles can be divided into four different group. These findings indicate the necessity of a more coherent taxonomic arrangement for the taxa of Ateles. Am. J. Primatol. 42:167–178, 1997. © 1997 Wiley-Liss, Inc.     

Comparative chromosomal study of five taxa of genus Callithrix,group Jacchus (Platyrrhini,primates)

The karyotypes of four marmoset species of the Callithrix jacchus group (C. aurita, C. kuhlii, C. geoffroyi, and C. penicillata) were investigated. The patterns of G-, C-, and NOR-bands of these karyotypes were compared with those of C. jacchus, previously described, in order to clarify the taxonomic relationships of this species group. All species present 2n = 46, 14 uni- and 30 biarmed autosomes, a median size submetacentric X chromosome, and the same NOR-band patterns. No rearrangement or constitutive heterochromatic variation differentiate these species, which differ only in the morphology of the Y chromosome. The data obtained indicate that, from the chromosomal point stand, the marmoset species of C. jacchus group constitute a homogeneous clade. Am J Primatol 41:53–60, 1997. © 1997 Wiley-Liss, Inc.     

Tonoplast intrinsic protein isoforms as markers for vacuolar functions

Plant cell vacuoles may have storage or lytic functions, but biochemical markers specific for the tonoplasts of functionally distinct vacuoles are poorly defined. Here, we use antipeptide antibodies specific for the tonoplast intrinsic proteins alpha-TIP, gamma-TIP, and delta-TIP in confocal immunofluorescence experiments to test the hypothesis that different TIP isoforms may define different vacuole functions. Organelles labeled with these antibodies were also labeled with antipyrophosphatase antibodies, demonstrating that regardless of their size, they had the expected characteristics of vacuoles. Our results demonstrate that the storage vacuole tonoplast contains delta-TIP, protein storage vacuoles containing seed-type storage proteins are marked by alpha- and delta- or alpha- and delta- plus gamma-TIP, whereas vacuoles storing vegetative storage proteins and pigments are marked by delta-TIP alone or delta- plus gamma-TIP. In contrast, those marked by gamma-TIP alone have characteristics of lytic vacuoles, and results from other researchers indicate that alpha-TIP alone is a marker for autophagic vacuoles. In root tips, relatively undifferentiated cells that contain vacuoles labeled separately for each of the three TIPs have been identified. These results argue that plant cells have the ability to generate and maintain three separate vacuole organelles, with each being marked by a different TIP, and that the functional diversity of the vacuolar system may be generated from different combinations of the three basic types.     

Insight into the molecular requirements for pathogenicity of Fusarium oxysporum f. sp. lycopersici through large-scale insertional mutagenesis

Background  

Fusarium oxysporum f. sp. lycopersici is the causal agent of vascular wilt disease in tomato. In order to gain more insight into the molecular processes in F. oxysporum necessary for pathogenesis and to uncover the genes involved, we used Agrobacterium-mediated insertional mutagenesis to generate 10,290 transformants and screened the transformants for loss or reduction of pathogenicity.     

Rates of nuclear and cytoplasmic mitochondrial DNA sequence divergence in mammals

Differential rates of nucleotide substitution among different gene segments and between distinct evolutionary lineages is well documented among mitochondrial genes and is likely a consequence of locus-specific selective constraints that delimit mutational divergence over evolutionary time. We compared sequence variation of 18 homologous loci (15 coding genes and 3 parts of the control region) among 10 mammalian mitochondrial DNA genomes which allowed us to describe different mitochondrial evolutionary patterns and to produce an estimation of the relative order of gene divergence. The relative rates of divergence of mitochondrial DNA genes in the family Felidae were estimated by comparing their divergence from homologous counterpart genes included in nuclear mitochondrial DNA (Numt, pronounced "new might"), a genomic fossil that represents an ancient transfer of 7.9 kb of mitochondrial DNA to the nuclear genome of an ancestral species of the domestic cat (Felis catus). Phylogenetic analyses of mitochondrial (mtDNA) sequences with multiple outgroup species were conducted to date the ancestral node common to the Numt and the cytoplasmic (Cymt) mtDNA genes and to calibrate the rate of sequence divergence of mitochondrial genes relative to nuclear homologous counterparts. By setting the fastest substitution rate as strictly mutational, an empirical "selective retardation index" is computed to quantify the sum of all constraints, selective and otherwise, that limit sequence divergence of mitochondrial gene sequences over time.      

Rapid evolution in a conserved gene family. Evolution of the actin gene family in the sea urchin genus Heliocidaris and related genera

Camarodont sea urchins possess a rapidly evolving actin gene family whose members are expressed in distinct cell lineages in a developmentally regulated fashion. Evolutionary changes in the actin gene family of echinoids include alterations in number of family members, site of expression, and gene linkage, and a dichotomy between rapidly and slowly evolving isoform-specific 3' untranslated regions. We present sequence comparisons and an analysis of the actin gene family in two congeneric sea urchins that develop in radically different modes, Heliocidaris erythrogramma and H. tuberculata. The sequences of several actin genes from the related species Lytechinus variegatus are also presented. We compare the features of the Heliocidaris and Lytechinus actin genes to those of the the actin gene families of other closely related sea urchins and discuss the nature of the evolutionary changes among sea urchin actins and their relationship to developmental mode.