Molecular evidence for repetitive parallel evolution of shell structure in Clausiliidae (Gastropoda, pulmonata)

The division of clausiliid genera, using the type of clausilial apparatus (CA) as the decisive criterion, is ambiguous. Two types of CA can be distinguished: the normal (N) type and the Graciliaria (G) type. Morphological resemblance between species with different types of CA led to the hypothesis that the CA type is homoplasious. Therefore sequence variation, phylogenetic relationships, and the evolution of the CA were studied in the genera Albinaria, Isabellaria, and Sericata. Phylogenetic relations were inferred from parsimony and neighbor-joining analyses of the nucleotide sequences of both internal transcribed spacers (ITS1 and ITS2) of the rDNA of 36 species. The variation among the sequences was great: 21.8% of the sequences were ambiguously aligned and excluded from the analysis. A high GC content in the unambiguously aligned portions and a substitutional bias toward a higher GC content are indicators of substitutional constraints in the spacers. We analyzed the data in several ways: using both spacers together and separately, weighting all mutations equally, correcting for transition/transversion bias by weighting, and using transversions only. In all resulting trees, Isabellaria is not a monophyletic group. Its division into two clades is supported by over 40 mutations and one large indel. Clade 1 consists of Isabellaria and Sericata and clade 2 consists of Isabellaria and Albinaria species. The present distribution of the CA type was plotted on the tree and its most parsimonious evolution was reconstructed. The CA type was shown to be highly homoplasious. In clade 1 and clade 2 both types of CA were found; depending on the ancestral state, either the G or the N type evolved several times in parallel. These results contribute decisively to the current debate on the morphological diagnoses of Albinaria, Sericata, and Isabellaria as monophyletic taxa.     

Zinc-dependent binding between peptides derived from rainbow trout CD8α and LCK

The cytoplasmic tail of mammalian CD8α binds the kinase LCK in a zinc-dependent manner. In analogy with a previous study for humans (Kim et al., 2003) peptides were synthesized from rainbow trout CD8α and LCK. Surface plasmon resonance (SPR) analysis indicated that also in fish these molecules bind to each other in a zinc-dependent manner.     

Satellite tracking of two Montagu’s Harriers (Circus pygargus): dual pathways during autumn migration

Autumn migration routes of two Dutch female Montagu’s Harriers (Circus pygargus) were documented for the first time using satellite telemetry. Both migrated to their African wintering area—one via the Straits of Gibraltar through the Mediterranean and the other via Italy/Tunisia. The rate of travel was comparable to values reported for larger raptor species.     

Drosophila melanogaster, a model system for comparative studies on the responses to real and simulated microgravity

A key requirement to enhance our understanding of the response of biological organisms to different levels of gravity is the availability of experimental systems that can simulate microgravity and hypergravity in ground-based laboratories. This paper compares the results obtained from analysing gene expression profiles of Drosophila in space versus those obtained in a random position machine (RPM) and by centrifugation. The correlation found validates the use of the RPM simulation technique to establish the effects of real microgravity on biological systems. This work is being extended to investigate Drosophila development in another gravity modifying instrument, the levitation magnet.     

The usefulness of the <Emphasis Type="Italic">gfp</Emphasis> reporter gene for monitoring <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation of potato dihaploid and tetraploid genotypes

Potato is one of the main targets for genetic improvement by gene transfer. The aim of the present study was to establish a robust protocol for the genetic transformation of three dihaploid and four economically important cultivars of potato using Agrobacterium tumefaciens carrying the in vivo screenable reporter gene for green fluorescent protein (gfp) and the marker gene for neomycin phosphotransferase (nptII). Stem and leaf explants were used for transformation by Agrobacterium tumefaciens strain LBA4404 carrying the binary vector pHB2892. Kanamycin selection, visual screening of GFP by epifluorescent microscopy, PCR amplification of nptII and gfp genes, as well as RT-PCR and Southern blotting of gfp and Northern blotting of nptII, were used for transgenic plant selection, identification and analysis. Genetic transformation was optimized for the best performing genotypes with a mean number of shoots expressing gfp per explant of 13 and 2 (dihaploid line 178/10 and cv. ‘Baltica’, respectively). The nptII marker and gfp reporter genes permitted selection and excellent visual screening of transgenic tissues and plants. They also revealed the effects of antibiotic selection on organogenesis and transformation frequency, and the identification of escapes and chimeras in all potato genotypes. Silencing of the gfp transgene that may represent site-specific inactivation during cell differentiation, occurred in some transgenic shoots of tetraploid cultivars and in specific chimeric clones of the dihaploid line 178/10. The regeneration of escapes could be attributed to either the protection of non-transformed cells by neighbouring transgenic cells, or the persistence of Agrobacterium cells in plant tissues after co-cultivation.     

Interactions between soil and tree roots accelerate long-term soil carbon decomposition

Decomposition of soil organic carbon (SOC) is the main process governing the release of CO₂ into the atmosphere from terrestrial systems. Although the importance of soil–root interactions for SOC decomposition has increasingly been recognized, their long-term effect on SOC decomposition remains poorly understood. Here we provide experimental evidence for a rhizosphere priming effect, in which interactions between soil and tree roots substantially accelerate SOC decomposition. In a 395-day greenhouse study with Ponderosa pine and Fremont cottonwood trees grown in three different soils, SOC decomposition in the planted treatments was significantly greater (up to 225%) than in soil incubations alone. This rhizosphere priming effect persisted throughout the experiment, until well after initial soil disturbance, and increased with a greater amount of root-derived SOC formed during the experiment. Loss of old SOC was greater than the formation of new C, suggesting that increased C inputs from roots could result in net soil C loss.     

Rapidly in situ-forming degradable hydrogels from dextran thiols through Michael addition

Thiol-functionalized dextrans (dex-SH) (M(n,dextran) = 14K or 31K) with degrees of substitution (DS) ranging from 12 to 25 were synthesized and investigated for in situ hydrogel formation via Michael type addition using poly(ethylene glycol) tetra-acrylate (PEG-4-Acr) or a dextran vinyl sulfone conjugate with DS 10 (dex-VS DS 10). Dex-SH was prepared by activation of the hydroxyl groups of dextran with 4-nitrophenyl chloroformate and subsequent reaction with cysteamine. Hydrogels were rapidly formed in situ under physiological conditions upon mixing aqueous solutions of dex-SH and either PEG-4-Acr or dex-VS DS 10 at polymer concentrations of 10 to 20 w/v%. Rheological studies showed that these hydrogels are highly elastic. By varying the DS, concentration, dextran molecular weight, and type of cross-linker, hydrogels with a broad range of storage moduli of 9 to 100 kPa could be obtained. Varying the ratio of thiol to vinyl sulfone groups from 0.9 to 1.1 did not alter the storage modulus of the hydrogels, whereas larger deviations from equimolarity (thiol to vinyl sulfone ratios of 0.75 and 1.5) considerably decreased the storage modulus. The plateau value of hydrogel storage modulus was reached much faster at pH 7.4 compared to pH 7, due to a higher concentration of the thiolate anion at higher pH. These hydrogels were degradable under physiological conditions. Degradation times were 3 to 7 weeks for dex-SH/dex-VS DS 10 hydrogels and 7 to over 21 weeks for dex-SH/PEG-4-Acr hydrogels, depending on the DS, concentration, and dextran molecular weight.     

Carbon efficiency for nutrient acquisition (CENA) by plants: role of nutrient availability and microbial symbionts

Plant and Soil - In a recent framework, Raven et al. New Phytologist 217: 1420-1427. (2018) considered carbon cost of acquiring phosphorus by mycorrhizal and non-mycorrhizal plants. We broaden...