Higher temperature reduces the effects of litter quality on decomposition by aquatic fungi

1. We investigated the effects of riparian plant diversity (species number and identity) and temperature on microbially mediated leaf decomposition by assessing fungal biodiversity, fungal reproduction and leaf mass loss. 2. Leaves of five riparian plant species were first immersed in a stream to allow microbial colonisation and were then exposed, alone or in all possible combinations, at 16 or 24 °C in laboratory microcosms. 3. Fungal biodiversity was reduced by temperature but was not affected by litter diversity. Temperature altered fungal community composition with species of warmer climate, such as Lunulospora curvula, becoming dominant. 4. Fungal reproduction was affected by litter diversity, but not by temperature. Fungal reproduction in leaf mixtures did not differ or was lower than that expected from the weighted sum of fungal sporulation on individual leaf species. At the higher temperature, the negative effect of litter diversity on fungal reproduction decreased with the number of leaf species. 5. Leaf mass loss was affected by the identity of leaf mixtures (i.e. litter quality), but not by leaf species number. This was mainly explained by the negative correlation between leaf decomposition and initial lignin concentration of leaves. 6. At 24 °C, the negative effects of lignin on microbially mediated leaf decomposition diminished, suggesting that higher temperatures may weaken the effects of litter quality on plant litter decomposition in streams. 7. The reduction in the negative effects of lignin at the higher temperature resulted in an increased microbially mediated litter decomposition, which may favour invertebrate‐mediated litter decomposition leading to a depletion of litter stocks in streams.     

Seed survival and dispersal of an endemic Atlantic forest palm: the combined effects of defaunation and forest fragmentation

About 45 palm species occur in the Atlantic forest of Brazil, and most of them are affected by loss of seed dispersers resulting from forest fragmentation and hunting. Here we report the effects of habitat loss and defaunation on the seed dispersal system of an endemic palm, Astrocaryum aculeatissimum . We evaluated seed removal, insect and rodent seed predation, and scatter-hoarding in nine sites, ranging from 19 ha to 79 000 ha. We report the seedling, juvenile and adult palm densities in this range of sites. Endocarps remaining beneath the parent palm had a higher probability of being preyed upon by insects in small, mostly fragmented and more defaunated sites. The frequency of successful seed removal, scatter-hoarding and consumption by rodents increased in the larger, less defaunated sites. Successful removal and dispersal collapsed in small (< 1000 ha), highly defaunated sites and frequently resulted in low densities of both seedlings and juveniles. Our results indicate that a large fraction of Atlantic forest palms that rely on scatter-hoarding rodents may become regionally extinct due to forest fragmentation and defaunation. Current management practices including palm extraction and hunting pressure have a lasting effect on Atlantic forest palm regeneration by severely limiting successful recruitment of prereproductive individuals. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 141–149.     

The filum terminale of the frog spinal cord,a nontransformed glial preparation: II. Uptake of serotonin

The uptake of 5-HT was measured in the frog filum terminale (FT), a preparation composed almost exclusively of normal glia. [³H]5-HT was taken up by the FT via a high-affinity, sodium-dependent, temperature-sensitive transport system having aK _m of 0.7 M. In addition, a variety of drugs and aromatic amines known to selectively inhibit 5-HT uptake by synaptosomes and brain slices affected the uptake of 5-HT by the FT in a qualitatively similar manner. The FT was shown to accumulate [³H]5-HT at rates significantly greater than the lumbar enlargement which contains both neurons and glia. The glial accumulation of 5-HT by the FT was verified by autoradiography. These findings strongly support the suggestion that glia may modulate aminergic transmission by competing with neurons for the reuptake of neuronally released amines.     

Zea systematics: ribosomal ITS evidence

Ribosomal internal transcribed spacer (ITS) sequences were used to evaluate the phylogenetics of Zea and Tripsacum. Maximum likelihood and polymorphism parsimony were used for phylogenetic reconstructions. Zea ITS nucleotide diversity was high compared to other plant species, but approximately equivalent to other maize loci. Coalescence of ITS alleles was rapid relative to other nuclear loci; however, there was still much diversity within populations. Zea and Tripsacum form a clade clearly differentiated from all other Poaceae. Four Zea ITS pseudogenes were identified by phylogenetic position and nucleotide composition. The phylogenetic position of Z. mays ssp. huehuetenangensis was clearly established as basal to the other Z. mays. The ITS phylogeny disfavored a Z. luxurians and Z. diploperennis clade, which conflicted with some previous studies. The introgression of Z. mays alleles into Z. perennis and Z. diploperennis was also established. The ITS data indicated a near contemporary divergence of domesticated maize and its two closest wild relatives.      

Leishmania donovani: characterization of a 38-kDa membrane protein that cross-reacts with the mammalian G-protein transducin

We investigated the presence in Leishmania donovani promastigotes of proteins with homology to the G-proteins known to mediate signal transduction in other organisms. [alpha 32P]GTP binding experiments revealed the presence in the promastigote membrane of GTP-binding sites with high affinity and specificity. Experiments with antisera directed against mammalian G-proteins showed that the promastigotes possess a 38-kDa protein (p38) which strongly reacts with an antiserum directed against a decapeptide containing the C-terminal sequence of transducin, the G-protein that mediates visual signal transduction. The interaction of p38 with the antiserum is specifically blocked by the decapeptide antigen. p38 is enriched in plasma membranes and is absent in cytosol and in a mitochondria-enriched fraction. p38 was also detected in two other Leishmania species, L. mexicana and L. major. The migration of p38 upon sucrose gradient centrifugation of detergent extract of L. donovani membranes corresponded to Mr of approximately 70,000, indicating that p38 is part of an oligomeric structure. The findings suggest that p38 may be a component of a transmembrane signal transduction system in Leishmania.     

Genomic complexity of the variable region-containing chitin-binding proteins in amphioxus

Background

Genetic isolates such as the Ashkenazi Jews (AJ) potentially offer advantages in mapping novel loci in whole genome disease association studies. To analyze patterns of genetic variation in AJ, genotypes of 101 healthy individuals were determined using the Affymetrix EAv3 500 K SNP array and compared to 60 CEPH-derived HapMap (CEU) individuals. 435,632 SNPs overlapped and met annotation criteria in the two groups.

Results

A small but significant global difference in allele frequencies between AJ and CEU was demonstrated by a mean F _ST of 0.009 (P < 0.001); large regions that differed were found on chromosomes 2 and 6. Haplotype blocks inferred from pairwise linkage disequilibrium (LD) statistics (Haploview) as well as by expectation-maximization haplotype phase inference (HAP) showed a greater number of haplotype blocks in AJ compared to CEU by Haploview (50,397 vs. 44,169) or by HAP (59,269 vs. 54,457). Average haplotype blocks were smaller in AJ compared to CEU (e.g., 36.8 kb vs. 40.5 kb HAP). Analysis of global patterns of local LD decay for closely-spaced SNPs in CEU demonstrated more LD, while for SNPs further apart, LD was slightly greater in the AJ. A likelihood ratio approach showed that runs of homozygous SNPs were approximately 20% longer in AJ. A principal components analysis was sufficient to completely resolve the CEU from the AJ.

Conclusion

LD in the AJ versus was lower than expected by some measures and higher by others. Any putative advantage in whole genome association mapping using the AJ population will be highly dependent on regional LD structure.