Delineating fine-scale genetic units in amphibians:Probing the primacy of ponds

The population structure of pond-breeding amphibians is shaped by their distinct breeding foci, but it is unclear to what extent this is reflected in the fine-scale distribution of genetic diversity. We used microsatellite genotypes to investigate the genetic signatures of 24 populations of European newts, Triturus cristatus and T. marmoratus, inhabiting 21 ponds in a confined study area (7.5×3.5km) in western France. Employing a Bayesian clustering approach based on individual genotypes that minimises departures from Hardy–Weinberg equilibrium and linkage disequilibrium, no evidence was found for within-pond substructuring. Subjecting all sampled ponds simultaneously to this procedure revealed a clear signal of partitioning, with the most likely number of clusters however below the actual number of ponds (seven in T. cristatus, three in T. marmoratus). A more hierarchical Bayesian approach, with pond as analysis unit, was achieved to separate ponds from genetically more meaningful units, and reduced the T. cristatus populations to 11 clusters, and the T. marmoratus populations to five clusters. We were unable to specify a minimum nearest-neighbour distance where ponds are separate units, probably due to both historical and current demographic processes. The implications for strategies to manage and conserve endangered amphibians in human-altered landscapes are discussed.     

Pre-pleistocene refugia and differentiation between populations of the caucasian salamander (Mertensiella caucasica)

A 350-bp fragment of the mitochondrial cytochrome-b gene was sequenced in the Caucasian salamander, Mertensiella caucasica, representing 10 populations from across its range along the Black Sea coast. Five haplotypes were discovered among 65 fragments analyzed, differing at 2-50 positions. The highest differentiation between haplotypes was observed in animals from the eastern part of the species' range (Borjomi) compared to those from the remainder of the species' range. Randomly amplified nuclear DNA revealed a pattern of spatial genetic variation similar to that of the mitochondrial genome. M. caucasica, as currently known, represents two evolutionary lineages that evolved independently, perhaps since the lower Pliocene. These lineages represent taxa, possibly to be described as species, distributed in the Borjomi area in central Georgia and in southwestern Georgia and northeastern Turkey. The multivariate analysis of morphological data did not reveal significant differences between the taxa. However, substantial morphological differentiation was observed within both lineages, showing parallel patterns in body proportions and coloration patterns. This variation is possibly associated with extant ecological conditions. Salamanders with reduced pigmentation from southwestern Georgia were not genetically distinguishable from neighboring populations.     

Chlorophyll proteins of photosystem I

Data are presented which suggest the existence of a light-harvesting pigment-protein complex which is functionally and structurally associated with photosystem I (PSI) reaction centers. These observations are based on techniques which allow isolation of PSI using minimal concentrations of Triton X-100. Properties of density and self aggregation allowed purification of a “native” PSI complex.     

Naturally acquired anthrax antibodies in a cheetah (Acinonyx jubatus) in Botswana

An outbreak of anthrax in the Jwana Game Reserve in Jwaneng, Botswana, was first observed when three cheetahs (Acinonyx jubatus) died of the disease in November 2004. In the aftermath of this event, banked serum samples collected from 23 wild-caught cheetahs were examined, by the inhibition enzyme-linked immunoassay (ELISA), for antibodies to the protective antigen (PA) of Bacillus anthracis. Of the 23 cheetahs, 16 regularly accessed the reserve. Antibodies to PA were detected in one cheetah collected in May 2004, indicating the disease was occurring well before it was first noticed. This appears to be the first demonstration of naturally acquired anthrax antibodies in cheetahs. The finding of one antibody-positive animal amongst at least 16 potentially exposed individuals is consistent with existing reports that it is uncommon for cheetahs to develop natural immunity to anthrax.     

Agrobacterium -mediated transformation of embryogenic cell suspensions of the banana cultivar Rasthali (AAB)

 A protocol was developed for establishing embryogenic suspension cultures from in vitro-grown, thin shoot-tip sections of the banana cultivar Rasthali. The best medium for callus induction was an MS-based medium supplemented with 2 mg/l 2,4-D and 0.2 mg/l zeatin. The callus was transferred to liquid medium to establish embryogenic cell suspensions. These cultures were subsequently used for Agrobacterium-mediated transformation. The Agrobacterium tumefaciens strain EHA105 containing the binary vector pVGSUN with the als gene as a selectable marker and an intron-containing the gusA gene as a reporter gene was used for transformations. The herbicide Glean was used as a selection agent. Two hundred putative transformants were recovered, of which a set of 16 was tested by histochemical analysis for GUS expression and by Southern blot analysis with a probe for the gusA gene. The plants were positive for GUS expression and integration of the gusA gene. Two of the transformants were grown to maturity under greenhouse conditions. Bananas were harvested to test GUS expression by histochemical analysis. The fruit from both transgenics tested positive for GUS expression. Received: 22 February 2000 / Revision received: 2 October 2000 / Accepted: 5 October 2000     

Postglacial species displacement in Triturus newts deduced from asymmetrically introgressed mitochondrial DNA and ecological niche models

ABSTRACT: BACKGROUND: If the geographical displacement of one species by another is accompanied by hybridization, mitochondrial DNA can introgress asymmetrically, from the outcompeted species into the invading species, over a large area. We explore this phenomenon using the two parapatric crested newt species, Triturus macedonicus and T. karelinii, distributed on the Balkan Peninsula in south-eastern Europe, as a model. RESULTS: We first delimit a ca. 54,000 km2 area in which T. macedonicus contains T. karelinii mitochondrial DNA. This introgression zone bisects the range of T. karelinii, cutting off a T. karelinii enclave. The high similarity of introgressed mitochondrial DNA haplotypes with those found in T. karelinii suggests a recent transfer across the species boundary. We then use ecological niche modeling to explore habitat suitability of the location of the present day introgression zone under current, mid-Holocene and Last Glacial Maximum conditions. This area was inhospitable during the Last Glacial Maximum for both species, but would have been habitable at the mid-Holocene. Since the mid-Holocene, habitat suitability generally increased for T. macedonicus, whereas it decreased for T. karelinii. CONCLUSION: The presence of a T. karelinii enclave suggests that T. karelinii was the first to colonize the area where the present day introgression zone is positioned after the Last Glacial Maximum. Subsequently, we propose T. karelinii was outcompeted by T. macedonicus, which captured T. karelinii mitochondrial DNA via introgressive hybridization in the process. Ecological niche modeling suggests that this replacement was likely facilitated by a shift in climate since the mid-Holocene. We suggest that the northwestern part of the current introgression zone was probably never inhabited by T. karelinii itself, and that T. karelinii mitochondrial DNA spread there through T. macedonicus exclusively. Considering the spatial distribution of the introgressed mitochondrial DNA and the signal derived from ecological niche modeling, we do not favor the hypothesis that foreign mitochondrial DNA was pulled into the T. macedonicus range by natural selection.     

ABNORMAL GUARD CELL DEVELOPMENT IN AN OLIVE NECROTIC MUTANT OF MAIZE

A study of a mutant variety of Zea mays (ON8147) revealed that the mutant plants, in contrast with normal maize plants, do not exhibit a light-induced increase in the rate of transpiration, and that the ontogeny of the stomatal complex is abnormal. In later stages of differentiation, the guard cells of mutant plants deteriorate, leaving the mature stomata with only the two subsidiary cells. The subsidiary cells in stomata of mutant leaves are similar to those of normal leaves with respect to their capacity to accumulate K⁺ in the dark, but they do not lose K⁺ in the light, as do subsidiary cells of stomata of nonmutant plants. It is suggested that impairment of guard cell function causes death of the mutant plant seedlings primarily by restricting CO₂ entry into the leaf.     

Plant cell factories and mucosal vaccines

Many advances continue to be made in the field of plant-derived vaccines. Plants have been shown capable of expressing a multicomponent vaccine that when orally delivered induces a T-helper cell subset 1 response and enables passive immunization. Furthermore, a plant-derived vaccine has been shown to protect against challenge in the target host. Increased antigen expression levels (up to 4.1% total soluble protein) have been obtained through transformation of the chloroplast genome. In view of these findings, plant-derived vaccines have been proved as valuable commodities to the world's health system; however, before their application, studies need to focus on optimization of immunization strategies and to investigate antigen stability.