Midsummer heat wave effects on lacustrine plankton: Variation of assemblage structure and fatty acid composition

The effects of the 2003 European heat wave on a freshwater plankton assemblage and its fatty acid (FA) composition were investigated. Composition and FA profiles of four size categories of planktonic organisms collected in 2003 were compared to those of the colder year 2002.     

Centrifugation of 2-cell mouse ova: cytoplasm stratification and recovery

Summary Two-cell mouse ova, which were centrifuged for l h at 70 000–90 000xg, showed a precise stratification of the cytoplasm and an elongation of the nucleus. The ova were fixed at different times and observed by light and electron microscopy using cytochemical methods and detergent extractions. Within 40 min after centrifugation the normal-looking morphology was recovered except for the persisting lipid caps at the centripetal poles of the blastomeres. Cleavage, compaction and blastulation were not prevented by centrifugation. Treatments with colcemid or cytochalasin D delayed but did not impair recovery. These results suggest that a resilient cytoskeletal structure may be involved in this kind of embryonic regulation.     

Ecophysiology and distribution of the endemic leafless spurgeEuphorbia aphylla and the introducedE. tirucalli (Euphorbiaceae,Euphorbia sect.Tirucalli) in the Canary Islands

The leafless spurgeEuphorbia aphylla (Euphorbiaceae), an endemic species restricted to several of the Canary Islands where it inhabits coastal and arid localities, expresses Crassulacean Acid Metabolism (CAM) when it is subjected to summer drought. A flexible CAM is consistent with the general ecology of the species. It is the only member of sect.Tirucalli native to the Canary Islands and is at the north-western edge of the section's biogeographical range. The other members of the section have a paleotropic distribution and are found throughout Africa. Many of them are regarded as obligate CAM plants, includingE. tirucalli which was used as a comparison in ecophysiological experiments examining the response ofE. aphylla to drought and temperature.     

Small-spored Alternaria spp. (section Alternaria) are common pathogens on wild tomato species

The wild relatives of modern tomato crops are native to South America. These plants occur in habitats as different as the Andes and the Atacama Desert and are, to some degree, all susceptible to fungal pathogens of the genus Alternaria. Alternaria is a large genus. On tomatoes, several species cause early blight, leaf spots and other diseases. We collected Alternaria-like infection lesions from the leaves of eight wild tomato species from Chile and Peru. Using molecular barcoding markers, we characterized the pathogens. The infection lesions were caused predominantly by small-spored species of Alternaria of the section Alternaria, like A. alternata, but also by Stemphylium spp., Alternaria spp. from the section Ulocladioides and other related species. Morphological observations and an infection assay confirmed this. Comparative genetic diversity analyses show a larger diversity in this wild system than in studies of cultivated Solanum species. As A. alternata has been reported to be an increasing problem in cultivated tomatoes, investigating the evolutionary potential of this pathogen is not only interesting to scientists studying wild plant pathosystems. It could also inform crop protection and breeding programs to be aware of potential epidemics caused by species still confined to South America.     

Three new species of penicillium

Three new species of microfungi belonging to the genus Penicillium Link ex Fries are described and illustrated. All but one have been isolated from the atmosphere of las Palmas, capital city of the island of Gran Canaria (Canary Islands, Spain). They clearly differ from all species of the genus described so far and are, therefore, described and proposed as new species: Penicillium hispanicum sp. nov., Penicillium grancanariae sp. nov., and Penicillium palmensis sp. nov.     

Mechanisms towards compensation of long-term haemopoietic injury in mice after 5 Gy irradiation:In vivo andin vitro enhancement of superoxide anion production by granulocytes

This paper analyzes the long-term (6 and 12 months) function of mouse granulocytes after total body irradiation with a single dose (5 Gy) of X-rays. Superoxide anion production has been investigated in granulocytes from peripheral blood, and also in those harvested from long term bone marrow cultures, with the aim of correlating the environmental damage induced by radiation with the functional properties of granulocytes. Anin vivo andin vitro enhancement of superoxide anion production and protein levels in granulocytes from irradiated mice is described. The presence of some colony stimulating factor in the supernatant of cultures from irradiated mice could play an important role in the priming of granulocytes.     

Vacuolar targeting of recombinant antibodies in Nicotiana benthamiana

Plant‐based platforms are extensively used for the expression of recombinant proteins, including monoclonal antibodies. However, to harness the approach effectively and leverage it to its full potential, a better understanding of intracellular processes that affect protein properties is required. In this work, we examined vacuolar (vac) targeting and deposition of the monoclonal antibody (Ab) 14D9 in Nicotiana benthamiana leaves. Two distinct vacuolar targeting signals (KISIA and NIFRGF) were C‐terminal fused to the heavy chain of 14D9 (vac‐Abs) and compared with secreted and ER‐retained variants (sec‐Ab, ER‐Ab, respectively). Accumulation of ER‐ and vac‐Abs was 10‐ to 15‐fold higher than sec‐Ab. N‐glycan profiling revealed the predominant presence of plant typical complex fucosylated and xylosylated GnGnXF structures on sec‐Ab while vac‐Abs carried mainly oligomannosidic (Man 7‐9) next to GnGnXF forms. Paucimannosidic glycans (commonly assigned as typical vacuolar) were not detected. Confocal microscopy analysis using RFP fusions showed that sec‐Ab‐RFP localized in the apoplast while vac‐Abs‐RFP were exclusively detected in the central vacuole. The data suggest that vac‐Abs reached the vacuole by two different pathways: direct transport from the ER bypassing the Golgi (Ab molecules containing Man structures) and trafficking through the Golgi (for Ab molecules containing complex N‐glycans). Importantly, vac‐Abs were correctly assembled and functionally active. Collectively, we show that the central vacuole is an appropriate compartment for the efficient production of Abs with appropriate post‐translational modifications, but also point to a reconsideration of current concepts in plant glycan processing.     

Phosphate-solubilizing peanut associated bacteria: screening for plant growth-promoting activities

Carbon and nitrogen are supplied by a variety of sources in the desert food web; both vascular and non-vascular plants and cyanobacteria supply carbon, and cyanobacteria and plant-associated rhizosphere bacteria are sources of biological nitrogen fixation. The objective of this study was to compare the relative influence of vascular plants and biological soil crusts on desert soil nematode and protozoan abundance and community composition. In the first experiment, biological soil crusts were removed by physical trampling. Treatments with crust removed had fewer nematodes and a greater relative ratio of bacterivores to microphytophages than treatments with intact crust. However, protozoa composition was similar with or without the presence of crusts. In a second experiment, nematode community composition was characterized along a spatial gradient away from stems of grasses or shrubs. Although nematodes generally occurred in increasing abundance nearer to plant stems, some genera (such as the enrichment-type Panagrolaimus) increased disproportionately more than others (such as the stress-tolerant Acromoldavicus). We propose that the impact of biological soil crusts and desert plants on soil microfauna, as reflected in the community composition of microbivorous nematodes, is a combination of carbon input, microclimate amelioration, and altered soil hydrology.     

Structure and evolution of the Cinful retrotransposon family of maize.

A maize cDNA clone was isolated by virtue of its intense hybridization to total maize genomic DNA, indicating homology to highly repetitive sequences. Genomic homologues were identified and subcloned from an adh1-bearing maize yeast artificial chromosome (YAC). Sequencing revealed that the expressed sequence was part of a Ty3-gypsy-type retrotransposon. We discovered and sequenced two complete retrotransposons of this family, and named them Cinful elements because they are members of a family of maize retrotransposons including Zeon-1 and the first plant transposable element sequenced, the solo long terminal repeat (LTR) called Cin1. All are defective, as Cinful-1 and Cinful-2 elements lack gag and Zeon-1 lacks pol homology. Despite the apparent lack of an intact "autonomous" element, the Cinful family has expanded to a copy number of about 18 000, representing just under 9% of the maize genome. Both point mutations and major rearrangements, including possible gene acquisition, differentiate members of the Cinful family. Cinful family members were found to have an unusual feature that we also observed in two other Ty3-class retrotransposons of teosinte and tobacco: related tandem repeats that separate their internal domains with a gag- or pol-containing homology from a 3' segment of unknown function. The conserved and variable features identified provide insights into the origin, mutational history, and functional components of this major constituent of the maize genome.     

Mba1, a membrane-associated ribosome receptor in mitochondria

The genome of mitochondria encodes a small number of very hydrophobic polypeptides that are inserted into the inner membrane in a cotranslational reaction. The molecular process by which mitochondrial ribosomes are recruited to the membrane is poorly understood. Here, we show that the inner membrane protein Mba1 binds to the large subunit of mitochondrial ribosomes. It thereby cooperates with the C-terminal ribosome-binding domain of Oxa1, which is a central component of the insertion machinery of the inner membrane. In the absence of both Mba1 and the C-terminus of Oxa1, mitochondrial translation products fail to be properly inserted into the inner membrane and serve as substrates of the matrix chaperone Hsp70. We propose that Mba1 functions as a ribosome receptor that cooperates with Oxa1 in the positioning of the ribosome exit site to the insertion machinery of the inner membrane.