Identification of Trypanosoma cruzi Zymodemes by Kinetoplast DNA Probes

Analysis of zymograms of extracts of Trypanosoma cruzi isolated from different hosts in Argentina allowed characterization of 12 zymodemes or "isozymic strains," only six of which were found in human patients. Two of these six zymodemes (Z1 and Z12) were widely distributed and found in more than 80% of human patients. These two "major natural clones" differed significantly in pathogenic activity. Because the groupings obtained by studying enzymes and kinetoplast DNA (kDNA) were similar, it is possible to identify the zymodeme by analyzing kDNA. A 290-bp fragment was amplified by PCR using primers for the sequences flanking the hypervariable regions of kDNA minicircles. Labeled probes for this fragment, prepared from Z1 and Z12 reference stocks, hybridized specifically with PCR-amplified kDNA from parasite stocks, allowing identification of zymodemes.     

Multiple Pleistocene refugia and Holocene range expansion of an abundant southwestern American desert plant species (Melampodium leucanthum,Asteraceae)

Pleistocene climatic fluctuations had major impacts on desert biota in southwestern North America. During cooler and wetter periods, drought‐adapted species were isolated into refugia, in contrast to expansion of their ranges during the massive aridification in the Holocene. Here, we use Melampodium leucanthum (Asteraceae), a species of the North American desert and semi‐desert regions, to investigate the impact of major aridification in southwestern North America on phylogeography and evolution in a widespread and abundant drought‐adapted plant species. The evidence for three separate Pleistocene refugia at different time levels suggests that this species responded to the Quaternary climatic oscillations in a cyclic manner. In the Holocene, once differentiated lineages came into secondary contact and intermixed, but these range expansions did not follow the eastwardly progressing aridification, but instead occurred independently out of separate Pleistocene refugia. As found in other desert biota, the Continental Divide has acted as a major migration barrier for M. leucanthum since the Pleistocene. Despite being geographically restricted to the eastern part of the species’ distribution, autotetraploids in M. leucanthum originated multiple times and do not form a genetically cohesive group.     

Effect of temperature and dark pretreatment on the germination of three species of Jamesonia (Pteridaceae,Polypodiopsida)

To study the influence of temperature on the germination ability of three species of Jamesonia (Jamesonia imbricata, Jamesonia scammaniae and Jamesonia rotundifolia), spores were cultured at 10°C, 15°C and 20°C. A temperature of 15°C was selected as representative of the natural annual average temperature of the paramo environment that Jamesonia species inhabit. In addition, a dark pretreatment of 2 days was tested to verify if germination was enhanced. The results indicated that germination of Jamesonia, considering the three species as a whole, is affected by temperature, but is independent of the dark treatment. All species showed higher and faster germination at 20°C, and exhibited a threshold minimum temperature around 10°C, below which germination is avoided or extremely low and delayed. This could suggest that spore germination in Jamesonia is adapted to establish gametophyte populations during frost‐free periods.     

Phylogenetic relationships of the pygmy rice rats of the genus Oligoryzomys Bangs, 1900 (Rodentia: Sigmodontinae)

Sequences from two mitochondrial genes (cytochrome b and NADH1) were used to produce a molecular phylogeny for 12 named and two undescribed species of the genus Oligoryzomys. All analyses placed Oligoryzomys microtis as the most basal taxon, a finding consistent with previous studies that suggested the west‐central Amazon as a centre of origin for the tribe Oryzomyini to which Oligoryzomys belongs. Biogeographically, this suggests that Oligoryzomys had a South American origin, and later advanced northwards, entering Central America and Mexico more recently. Different analyses have provided consistent support for several additional clades that did not necessarily agree with the species groups hypothesized by previous studies. A molecular clock derived for these data suggests an origin for the genus of 6.67 Mya, with most speciation within the genus occurring between 3.7 and 1.5 Mya. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 551–566.     

Cell Surface Carbohydrate Differences in Wild and Mutant Strains of Crithidia fasciculata1

Wild type Crithidia fasciculata and three drug-resistant mutant strains that have shown “flagellar adherence” were studied as to their ability to agglutinate with lectins specific for receptor molecules containing N-acetyl glucosamine, N-acetyl galactosamine, galactose, mannose-like residues, fucose, and sialic acid. Escherichia coli with mannose-sensitive fimbriae was also used as an agglutination probe. The presence of D-GalNAc, D-Gal, and mannose-like residues was detected in the wild strain. Generally, in the mutants, residues of these sugar units were present in greater concentrations when compared to the wild type strain. β-Galactosidase treatment showed that β-D-Galp units are exposed on the cell membrane. All types of cell agglutination including flagellum-flagellum (F-F), flagellum-soma (F-S), and soma-soma (S-S) were observed when lectins were used; however, with E. coli only the F-F type of cell agglutination was observed with the wild type strain and the TFR^R1 mutant. All types of agglutination were observed with the other two mutants.     

New polymorphic microsatellite markers for California sea lions (Zalophus californianus)

Nine microsatellite loci were isolated and characterized from California sea lions (Zalophus californianus). In addition, two of five loci tested from harbour seal (Phoca vitulina) produced a single, clear band in Z. californianus, as did one out of five loci from grey seal (Halichoerus grypus) and one out of two loci from elephant seal (Mirounga sp.). No locus tested from South American fur seal (Arctocephalus australis) amplified in Z. californianus. Locus variability was assessed in California sea lions from Los Islotes rookery, Baja California Sur, Mexico. All loci were variable, with allele numbers ranging from three to 12.     

Tetraploid Rangpur lime rootstock increases drought tolerance via enhanced constitutive root abscisic acid production

Whole‐genome duplication, or polyploidy, is common in many plant species and often leads to better adaptation to adverse environmental condition. However, little is known about the physiological and molecular determinants underlying adaptation. We examined the drought tolerance in diploid (2x) and autotetraploid (4x) clones of Rangpur lime (Citrus limonia) rootstocks grafted with 2x Valencia Delta sweet orange (Citrus sinensis) scions, named V/2xRL and V/4xRL, respectively. Physiological experiments to study root–shoot communication associated with gene expression studies in roots and leaves were performed. V/4xRL was much more tolerant to water deficit than V/2xRL. Gene expression analysis in leaves and roots showed that more genes related to the response to water stress were differentially expressed in V/2xRL than in V/4xRL. Prior to the stress, when comparing V/4xRL to V/2xRL, V/4xRL leaves had lower stomatal conductance and greater abscisic acid (ABA) content. In roots, ABA content was higher in V/4xRL and was associated to a greater expression of drought responsive genes, including CsNCED1, a pivotal regulatory gene of ABA biosynthesis. We conclude that tetraploidy modifies the expression of genes in Rangpur lime citrus roots to regulate long‐distance ABA signalling and adaptation to stress.