Diversity and temporal stability of bacterial communities in a model passerine bird, the zebra finch

The composition and dynamics of the gastrointestinal bacterial communities in birds is determined by both host-specific and environmental exposure factors yet these are poorly understood. We selected the zebra finch, Taeniopygia guttata, as the host species to examine the diversity and temporal stability of the faecal microflora in a bird, owing to its importance as a model organism in avian ecology, neuroscience and evolution studies. The stability of the gut bacterial community of individual male and female zebra finches was assessed through repeat faecal sampling via culture and temperature gradient gel electrophoresis and partial sequencing of PCR-amplified eubacterial 16S rRNA gene products. Nineteen bacterial genera were detected across all samples (n = 99), with each bird carrying on average six operational taxonomic units. Using a novel statistical approach, we showed that bacterial assemblages and community richness varied between individual birds but remained stable over time within individuals. Neither the composition nor richness of bacterial communities differed significantly between the sexes. Our results show that zebra finches housed together under controlled conditions show consistent variation between individuals in their gut microflora that is not attributable to differences in host exposure to environmental microbial sources. Future studies could usefully explore the origin of this individual-specific variation and its consequences for host fitness and sexual selection.     

Amplification of a Cytochrome P450 Gene Is Associated with Resistance to Neonicotinoid Insecticides in the Aphid Myzus persicae

The aphid Myzus persicae is a globally significant crop pest that has evolved high levels of resistance to almost all classes of insecticide. To date, the neonicotinoids, an economically important class of insecticides that target nicotinic acetylcholine receptors (nAChRs), have remained an effective control measure; however, recent reports of resistance in M. persicae represent a threat to the long-term efficacy of this chemical class. In this study, the mechanisms underlying resistance to the neonicotinoid insecticides were investigated using biological, biochemical, and genomic approaches. Bioassays on a resistant M. persicae clone (5191A) suggested that P450-mediated detoxification plays a primary role in resistance, although additional mechanism(s) may also contribute. Microarray analysis, using an array populated with probes corresponding to all known detoxification genes in M. persicae, revealed constitutive over-expression (22-fold) of a single P450 gene (CYP6CY3); and quantitative PCR showed that the over-expression is due, at least in part, to gene amplification. This is the first report of a P450 gene amplification event associated with insecticide resistance in an agriculturally important insect pest. The microarray analysis also showed over-expression of several gene sequences that encode cuticular proteins (2–16-fold), and artificial feeding assays and in vivo penetration assays using radiolabeled insecticide provided direct evidence of a role for reduced cuticular penetration in neonicotinoid resistance. Conversely, receptor radioligand binding studies and nucleotide sequencing of nAChR subunit genes suggest that target-site changes are unlikely to contribute to resistance to neonicotinoid insecticides in M. persicae.     

New insights into the early biochemical activation of jasmonic acid biosynthesis in leaves

In plants, herbivore attack elicits the rapid accumulation of jasmonic acid (JA) which results from the activation of constitutively expressed biosynthetic enzymes. The molecular mechanisms controlling the activation of JA biosynthesis remain largely unknown however new research has elucidated some of the early regulatory components involved in this process. Nicotiana attenuata plants, a wild tobacco species, responds to fatty acid amino acid conjuguates (FAC) elicitors in the oral secretion of its natural herbivore, Manduca sexta, by triggering specific defense and tolerance responses against it; all of the defense responses known to date require the amplification of the wound-induced JA increase. We recently demonstrated that this FAC-elicited JA burst requires an increased flux of free linolenic acid (18:3) likely originating from the activation of a plastidial glycerolipase (GLA1) which is activated by an abundant FAC found in insect oral secretions, N-linolenoyl-glutamate (18:3-Glu). The lack of accumulation of free 18:3 after elicitation suggests a tight physical association between GLA1 and LOX3 in N. attenuata leaves. In addition, the salicylate-induced protein kinase (SIPK) and the nonexpressor of PR-1 (NPR1) participate in this activation mechanism that controls the supply of 18:3. In contrast, the wound-induced protein kinase (WIPK) does not but instead regulates the conversion of 13(S)-hydroperoxy-18:3 into 12-oxo-phytodienoic acid (OPDA). These results open new perspectives on the complex network of signals and regulatory components inducing the JA biosynthetic pathway.Key words: jasmonic acid, lipase, lipoxygenase, wounding, plant-insect interactions, FAC     

Patterns of genotype-by-environment interaction in diameter at breast height at age 3 for eucalypt hybrid clones grown for reafforestation of lands affected by salinity

The commercial viability of plantations established for the recovery of saline lands may be supported by the deployment of improved genetic material matched to these particularly challenging environments. Patterns of genotype-by-environment interaction were investigated in a highly unbalanced data set of diameter at breast height at approximately 3 years for a total of 841 genotypes from ten Eucalyptus camaldulensis × Eucalyptus globulus and Eucalyptus camaldulensis × Eucalyptus grandis hybrid families assessed across 21 trials grown on a range of saline and non-saline low rainfall sites from southeast Queensland through central NSW, Victoria, Tasmania and southeast South Australia to southwest Western Australia using factor-analytic mixed-model methods. There was significant heterogeneity among trials in estimates of family variance, genotype-within-family variance, the ratio of family variance to total genetic variance and individual broad-sense heritability. Cluster analyses indicated that family effects were highly correlated across a main group of 19 trials and that most trials fell into two major groups for genotype-within-family effects, with an average correlation among trials within these groups of 0.55. There was, however, no obvious geographical or other explanation for the patterns, suggesting that genotypes should be deployed on the basis of broad-scale adaptation.     

The pigments from Pinnacle Point Cave 13B, Western Cape, South Africa

Earth pigments from the three excavations at Pinnacle Point Cave 13B (Western Cape Province, South Africa), spanning the terminal middle Pleistocene and earlier late Pleistocene, are described and analyzed. Qualitative geological categorization primarily rested on textural, fabric, and iron enrichment attributes. Comprehensive recovery allowed identification of non-anthropic pigmentaceous materials, questionable pigments, and 380 pigments (1.08?kg). Less chemically altered pigments were typically fine-grained sedimentary (FGS) rocks, tending to be soft, highly micaceous, prone to laminar fragmentation, and with reddish-brown streaks of intermediate nuance. More iron-enriched forms tended to be harder, denser, poorly micaceous, and with redder streaks of more saturated nuance. Some still qualified as FGS forms, but a large number were categorized as sandstone or iron oxide. Despite some temporal change in raw material profiles, circumstantial evidence suggests primarily local procurement from one outcrop throughout the sequence. Definitely utilized pieces (12.7%) were overwhelmingly ground. Unusual forms of modification include several notched pieces and a deliberately scraped 'chevron.' Controlling for fragmentation, streak properties of utilized versus unutilized pieces were used to investigate selective criteria. There was robust evidence for preferential grinding of the reddest materials, strongly suggestive evidence for saturation and darkness being subordinate selective criteria, and some indication of more intensive grinding of materials with the reddest, most saturated, and darkest streaks, and for some deliberate heating of pigments. These findings challenge the initial stages of color lexicalization predicted by the various versions of the basic color term (BCT) hypothesis, they provide grounds for rejecting hafting as a general explanatory hypothesis, and they cannot be accounted for by incidental heating. The results are more consistent with agreed upon canons of ornamentation than with individual display. It is concluded that the material was processed to produce saturated red pigment powders. On theoretical grounds, these are presumed to have served primarily as body paints in ritual performance.