Subcellular localization of ubiquitin in plant protoplasts and the function of ubiquitin in selective degradation of outer-wall plasmodesmata in regenerating protoplasts

Immunocytochemical localizations in Vicia faba L. protoplasts and cultures of regenerating Solanum nigrum L. protoplasts support former observations that in plant cells ubiquitin occurs within the cytoplasm, the nucleus, the chloroplasts and at the plasmalemma, but not within the vacuole or the cell wall. Immunoresponses were also observed within mitochondria and associated with the endoplasmic reticulum, which is in accordance with previous findings on animal cells. Moreover, the tonoplast membrane system was found to be labelled. For regenerating S. nigrum protoplasts, evidence is given that ubiquitin plays a role in selective degradation even of whole subcellular structures. Most of the discontinuous plasmodesmata formed in the newly deposited outer cell walls during the early stages of culture disappear later on, except for those near the periphery of division walls or of non-division walls, which are probably used for the formation of continuous cell connections during further culture. Outer-wall plasmodesmata which are destined to disappear show high immunoreactivity to ubiquitin antibody, but no conspicuous immunolabelling was observed with the remaining plasmodesmata. Thus, the selective disintegration of whole plasmodesmatal structures is obviously regulated by ubiquitination of plasmodesmatal proteins. A model for the mechanism of degradation of outer-wall plasmodesmata during extension growth of the cell wall is presented.Dedicated to Professor Dr. Andreas Sievers on the occasion of his retirementThis work was supported by grants to R. K. (Deutsche Forschungsgemeinschaft) and to M. S. (Bennigsen-Foerder Preis des Landes Nordrhein-Westfalen). We thank Dipl.— Biol. Kirsten Leineweber for help with the V. faba protoplast isolation and Dr. Olaf Parge, Institut für Psychologie und Sozialforschung, Kiel, Germany, for giving assistance with the statistical analysis.     

Species-specific antigens ofMycoplasma hyopneumoniae and cross-reactions with other porcine mycoplasmas

Cell proteins from the porcine mycoplasmasMycoplasma hyorhinis, M. hyopneumoniae, andM. flocculare have been analyzed by SDS-gel electrophoresis and immunoblotting. The protein profiles ofM. hyopneumoniae andM. flocculare were similar, but the protein profile ofM. hyorhinis was quite different from the others. Antisera prepared against whole cells of the above three mycoplasmas were used in immunoblotting of electrophoretically separated antigens and in enzyme-linked immunosorbent assay. One major antigen, which had a molecular weight of 73 k, was found to be common to all three mycoplasmas. Another major antigen, with a molecular weight of 41 k, was common toM. hyopneumoniae andM. flocculare and may also be present inM. hyorhinis. Several antigens of comparatively high molecular weights (108 k, 102 k, 93 k, 89 k, and 87 k) seemed to be specific forM. hyopneumoniae. Three antisera prepared by immunization of rabbits with immunoprecipitates obtained by crossed immunoelectrophoresis ofM. hyopneumoniae were also used in blotting experiments. One of these antisera was found to be directed against the 73 k antigen common to the three porcine mycoplasmas investigated. The other two antisera were directed againstM. hyopneumoniae-specific antigens with molecular weights of 74 k, 58 k, 45 k, 44 k, and 38 k.     

All or nothing: Switch to high current reproductive investment under risk of starvation in male kelp crab

One of the key features in reproduction of polygynous species is seminal recovery after mating. However, it is poorly known how environmental factors affect the recuperation period of seminal material. This study aims to test plasticity in recovery of seminal reserves in response to distinct environmental conditions of the kelp crab Taliepus dentatus. Male crabs were maintained after depletion of seminal reserves in one of eight different treatments in a factorial design of temperature (12 and 16°C), food availability (with alimentation and food deprivation), and time period (15 and 30 days), simulating different environmental situations in the laboratory to which the crab might be exposed to along its distribution. Temperature and food availability modulated the seminal recovery period in T. dentatus. Complete replenishment was reached within 30 days in all treatments (i.e., 12 and 16°C each with alimentation and food deprivation), but the highest recovery index was found in crabs without food provision (16°C). In this condition, the recovery index was twice as high compared with males maintained at a similar temperature but with feeding. Prolonged starvation at 16°C may be extremely stressful conditions for male crabs, during which risk to die probably triggered a concentration of the reproductive effort in favor of immediate reproduction. This suggests that plasticity of energy allocation toward reproduction may be expressed during extremely suboptimal conditions, which might be a similar strategy as proposed by the terminal investment hypothesis. The generally relatively fast seminal recovery regardless of the temperature may explain the kelp crab's continuous mating throughout the year.     

Structure of the Cyanobacterial Phytochrome 2 Photosensor Implies a Tryptophan Switch for Phytochrome Signaling

Phytochromes are highly versatile photoreceptors, which occur ubiquitously in plants as well as in many light-responsive microorganisms. Here, photosynthetic cyanobacteria utilize up to three different phytochrome architectures, where only the plant-like and the single-domain cyanobacteriochromes are structurally characterized so far. Cph2 represents a third group in Synechocystis species and affects their capability of phototaxis by controlling c-di-GMP synthesis and degradation. The 2.6-Å crystal structure of its red/far-red responsive photosensory module in the P_r state reveals a tandem-GAF bidomain that lacks the figure-of-eight knot of the plant/cph1 subfamily. Its covalently attached phycocyanobilin chromophore adopts a highly tilted ZZZssa conformation with a novel set of interactions between its propionates and the GAF1 domain. The tongue-like protrusion from the GAF2 domain interacts with the GAF1-bound chromophore via its conserved PRXSF, WXE, and W(G/A)G motifs. Mutagenesis showed that the integrity of the tongue is indispensable for P_r → P_fr photoconversion and involves a swap of the motifs'' tryptophans within the tongue-GAF1 interface. This “Trp switch” is supposed to be a crucial element for the photochromicity of all multidomain phytochromes.     

Ablation of RIC8A Function in Mouse Neurons Leads to a Severe Neuromuscular Phenotype and Postnatal Death

Resistance to inhibitors of cholinesterase 8 (RIC8) is a guanine nucleotide exchange factor required for the intracellular regulation of G protein signalling. RIC8 activates different Gα subunits via non-canonical pathway, thereby amplifying and prolonging the G protein mediated signal. In order to circumvent the embryonic lethality associated with the absence of RIC8A and to study its role in the nervous system, we constructed Ric8a conditional knockout mice using Cre/loxP technology. Introduction of a synapsin I promoter driven Cre transgenic mouse strain (SynCre) into the floxed Ric8a (Ric8a ^F/F) background ablated RIC8A function in most differentiated neuron populations. Mutant SynCre ^+/- Ric8 ^lacZ/F mice were born at expected Mendelian ratio, but they died in early postnatal age (P4-P6). The mutants exhibited major developmental defects, like growth retardation and muscular weakness, impaired coordination and balance, muscular spasms and abnormal heart beat. Histological analysis revealed that the deficiency of RIC8A in neurons caused skeletal muscle atrophy and heart muscle hypoplasia, in addition, the sinoatrial node was misplaced and its size reduced. However, we did not observe gross morphological changes in brains of SynCre ^+/- Ric8a ^lacZ/F mutants. Our results demonstrate that in mice the activity of RIC8A in neurons is essential for survival and its deficiency causes a severe neuromuscular phenotype.     

Multifunctional floodplain management and biodiversity effects: a knowledge synthesis for six European countries

Floodplain ecosystems are biodiversity hotspots and supply multiple ecosystem services. At the same time they are often prone to human pressures that increasingly impact their intactness. Multifunctional floodplain management can be defined as a management approach aimed at a balanced supply of multiple ecosystem services that serve the needs of the local residents, but also those of off-site populations that are directly or indirectly impacted by floodplain management and policies. Multifunctional floodplain management has been recently proposed as a key concept to reconcile biodiversity and ecosystem services with the various human pressures and their driving forces. In this paper we present biophysics and management history of floodplains and review recent multifunctional management approaches and evidence for their biodiversity effects for the six European countries Ireland, the Netherlands, Germany, Slovakia, Hungary and the Ukraine. Multifunctional use of floodplains is an increasingly important strategy in some countries, for instance in the Netherlands and Hungary, and management of floodplains goes hand in hand with sustainable economic activities resulting in flood safety and biodiversity conservation. As a result, biodiversity is increasing in some of the areas where multifunctional floodplain management approaches are implemented. We conclude that for efficient use of management resources and ecosystem services, consensual solutions need to be realized and biodiversity needs to be mainstreamed into management activities to maximize ecosystem service provision and potential human benefits. Multifunctionality is more successful where a broad range of stakeholders with diverse expertise and interests are involved in all stages of planning and implementation.