Are Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl. migratory relicts?

It remains unclear why there are only two vascular plant species in Antarctica, Deschampsia antarctica Desv. (Poaceae) and Colobanthus quitensis (Kunth) Bartl. (Caryophyllaceae). Despite progressing climate warming, there is also just one alien plant species found in the region, introduced by humans and spreading mainly in disturbed habitats. In the present article we try to interpret the data concerning the history of the biota and glaciations of the continent, proceeding from the assumption that both plants migrated to Antarctica during the Oligocene-Pliocene, when it was less isolated and the climate was more favorable for their naturalization. Genetic evidence was also taken into consideration. Our data allow suggesting secondary dispersal in the region, due to transfer by birds with regard of climate changes. With this in mind, we believe that D. antarctica and C. quitensis are migratory relicts.     

The influence of some environmental factors on cytological and biometric parameters and chlorophyll content of Deschampsia antarctica Desv. in the maritime Antarctic

Under the environmental conditions of the Point Thomas Oasis (King George Island, the South Shetland Islands), we studied the influence of month-long artificial treatment with fresh water, salt water, and guano solution on the biometric characteristics, chlorophyll content, as well as the nuclear area of leaf parenchymal cells and nuclear DNA content, in a maritime Antarctic aboriginal plant Deschampsia antarctica. The modeled factors induced an increase in the generative shoot height and the length of the largest leaf, but did not influence the number of flowers. Treatment with guano caused an increase in the chlorophyll a and b contents, while fresh water treatment only led to some increase in chlorophyll a. Fluctuations of physiologically significant traits, such as the nuclear area and DNA content in the leaf parenchyma cells of D. antarctica, have been traced under the influence of the studied factors. Understanding of the hierarchy of influence of these factors as well as and sensitivity of plants of this species to external agents require further investigation.     

Impact of methionine oxidation as an initial event on the pathway of human prion protein conversion

Prion diseases comprise a group of fatal neurodegenerative disorders characterized by the autocatalytic conversion of the cellular prion protein PrP^C into the infectious misfolded isoform PrP^Sc. Increasing evidence supports a specific role of oxidative stress in the onset of pathogenesis. Although the associated molecular mechanisms remain to be elucidated in detail, several studies currently suggest that methionine oxidation already detected in misfolded PrP^Sc destabilizes the native PrP fold as an early event in the conversion pathway. To obtain more insights about the specific impact of surface-exposed methionine residues on the oxidative-induced conversion of human PrP we designed, produced, and comparatively investigated two new pseudosulfoxidation mutants of human PrP 121–231 that comprises the well-folded C-terminal domain. Applying circular dichroism spectroscopy and dynamic light scattering techniques we showed that pseudosulfoxidation of all surface exposed Met residues formed a monomeric molten globule-like species with striking similarities to misfolding intermediates recently reported by other groups. However, individual pseudosulfoxidation at the polymorphic M129 site did not significantly contribute to the structural destabilization. Further metal-induced oxidation of the partly unfolded pseudosulfoxidation mutant resulted in the formation of an oligomeric state that shares a comparable size and stability with PrP oligomers detected after the application of different other triggers for structural conversion, indicating a generic misfolding pathway of PrP. The obtained results highlight the specific importance of methionine oxidation at surface exposed residues for PrP misfolding, strongly supporting the hypothesis that increased oxidative stress could be one causative event for sporadic prion diseases and other neurodegenerative disorders.     

Comprehensive characterization of cultivated in vitro <Emphasis Type="Italic">Deschampsia antarctica</Emphasis> E. Desv. plants with different chromosome numbers

D. antarctica E. Desv. plants cultivated in vitro were analyzed for the chromosome number, leaf length, and efficiency of callus formation. Most of the studied plants had a typical diploid chromosome number. However, a hypotriploid and a plant with B chromosomes demonstrated mixoploidy caused by the presence of a significant proportion (up to 15–25%) of aneuploid cells. Jaccard genetic distances between the plants determined from the data of ISSR- and IRAP-PCR analyses were within the range of 0.0323 to 0.1803. Furthermore, genetic distances between the specimens with atypical karyotype and diploids did not exceed the paired distances within the group of diploid plants. Variations in the leaf length and growth parameters of the plants were characterized. Plants with different chromosome numbers differed in the leaf length and efficiency of callus formation. Obtained results may indicate relationships between the chromosome number, studied morphometric parameters, and efficiency of callus formation in the analyzed D. antarctica plants.     

Are <Emphasis Type="Italic">Deschampsia antarctica</Emphasis> Desv. and <Emphasis Type="Italic">Colobanthus quitensis</Emphasis> (Kunth) Bartl. Migratory relicts?

It remains unclear why there are only two vascular plant species in Antarctica, Deschampsia antarctica Desv. (Poaceae) and Colobanthus quitensis (Kunth) Bartl. (Caryophyllaceae). Despite progressing climate warming, there is also just one alien plant species found in the region, introduced by humans and spreading mainly in disturbed habitats. In the present article, we try to interpret the data concerning the history of the biota and glaciations of the continent, proceeding from the assumption that both plants migrated to Antarctica during the Oligocene-Pliocene, when it was less isolated and the climate was more favorable for their naturalization. Genetic evidence was also taken into consideration. Our data allow the suggestion of secondary dispersal in the region, due to transference by birds with regard to climate changes. With this in mind, we believe that D. antarctica and C. quitensis are migratory relicts. The text was submitted by the authors in English.     

The influence of some environmental factors on cytological and biometric parameters and chlorophyll content of <Emphasis Type="Italic">Deschampsia antarctica</Emphasis> Desv. in the maritime Antarctic

Under the environmental conditions of the Point Thomas Oasis (King George Island, the South Shetland Islands), we studied the influence of month-long artificial treatment with fresh water, salt water, and guano solution on the biometric characteristics, chlorophyll content, as well as the nuclear area of leaf parenchymal cells and nuclear DNA content, in a maritime Antarctic aboriginal plant Deschampsia antarctica. The modeled factors induced an increase in the generative shoot height and the length of the largest leaf but did not influence the number of flowers. Treatment with guano caused an increase in the chlorophyll a and b contents, while fresh water treatment only led to some increase in chlorophyll a. Fluctuations of physiologically significant traits, such as the nuclear area and DNA content in the leaf parenchyma cells of D. antarctica, have been traced under the influence of the studied factors. Understanding of the hierarchy of influence of these factors as well as and sensitivity of plants of this species to external agents require further investigation.     

Adaptation of the seed reproduction system to conditions of Maritime Antarctic in <Emphasis Type="Italic">Deschampsia antarctica</Emphasis> E. Desv.

Deschampsia antarctica3 E. Desv. is one of the two flowering plants that, along with Colobanthus quitensis (Kunth) Bartl., was able to settle the ice-free areas of Antarctica. In order to identify the possible adaptations of the D. antarctica reproductive system to adverse environmental conditions, comparative cytoembryological analysis of plants of this species growing on the Antarctic Peninsula with plants of the closely related species D. beringensis Hult. from the Kamchatka Peninsula was conducted. It was found that both species are characterized by sexual mode of reproduction, equal size of pollen grains (25.5 ± 2.2 and 26.2 ± 1.9 μm, respectively), same features of the embryo sac structure, and emryo- and endospermogenesis. Interspecies differences have been found in mature embryo sac size (326.8 ± 12.8 and 161.7 ± 10.4 μm), pollen sterility percentage (86.1 ± 8.9 and 35.3 ± 9.2%), and quantity of pollen in the anthers (140 ± 15.3 and 1578 ± 88.6). Possible causes and significance of these differences are discussed. No unique adaptations of seed reproduction system that are inherent exclusively to D. antarctica were found. The D. antarctica reproduction strategy is based on the combination of autogamy (and its extreme form cleistogamy) with production of excess pollen quantity for its mode of pollination.     

Population-genetic analysis of Deschampsia antarctica from two regions of maritime antarctica

Comparative analysis of the sequence of the ITS1-2 rDNA region of Deschampsia antarctica showed that plants of this species with different genotypes may have migrated into Antarctica after the glacial period. The use of RAPD markers allowed the identification of differences at the level of polymorphisms between populations of D. antarctica located in different latitudes and showed a limitation of exchange of genetic material between these populations.     

Use of Deschampsia antarctica for nest building by the kelp gull in the Argentine Islands area (maritime Antarctica) and its possible role in plant dispersal

During the last 50?years, the western coast of the Antarctic Peninsula and adjacent archipelagos, also known as the maritime Antarctic, has experienced notable climate warming. As a result, expansion of the local distributions of the two native species of vascular plants, Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth.) Bartl., over previously unoccupied ground has been noted. Birds have been suggested to be partially responsible for this spread. The focus of the present study was to document the use of vascular plants in nest building by the kelp gull (Larus dominicanus) in the Argentine Islands region. During the 2009/2010 season, samples from kelp gull nests were collected and analyzed. Besides nests, material lost by birds during transfer was also studied. We demonstrate that, in the Argentine Islands region, Deschampsia antarctica and some bryophytes contribute the majority of nest building material for the kelp gull. Other materials, including lichens, gull feathers, and limpet shells, are used less frequently. The plants can reestablish upon transfer via vegetative or generative means. It thus seems that the kelp gull may potentially serve as a dispersal agent for Deschampsia antarctica.