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     

Common genetic variants and modification of penetrance of BRCA2-associated breast cancer

The considerable uncertainty regarding cancer risks associated with inherited mutations of BRCA2 is due to unknown factors. To investigate whether common genetic variants modify penetrance for BRCA2 mutation carriers, we undertook a two-staged genome-wide association study in BRCA2 mutation carriers. In stage 1 using the Affymetrix 6.0 platform, 592,163 filtered SNPs genotyped were available on 899 young (<40 years) affected and 804 unaffected carriers of European ancestry. Associations were evaluated using a survival-based score test adjusted for familial correlations and stratified by country of the study and BRCA2*6174delT mutation status. The genomic inflation factor (λ) was 1.011. The stage 1 association analysis revealed multiple variants associated with breast cancer risk: 3 SNPs had p-values<10(-5) and 39 SNPs had p-values<10(-4). These variants included several previously associated with sporadic breast cancer risk and two novel loci on chromosome 20 (rs311499) and chromosome 10 (rs16917302). The chromosome 10 locus was in ZNF365, which contains another variant that has recently been associated with breast cancer in an independent study of unselected cases. In stage 2, the top 85 loci from stage 1 were genotyped in 1,264 cases and 1,222 controls. Hazard ratios (HR) and 95% confidence intervals (CI) for stage 1 and 2 were combined and estimated using a retrospective likelihood approach, stratified by country of residence and the most common mutation, BRCA2*6174delT. The combined per allele HR of the minor allele for the novel loci rs16917302 was 0.75 (95% CI 0.66-0.86, ) and for rs311499 was 0.72 (95% CI 0.61-0.85, ). FGFR2 rs2981575 had the strongest association with breast cancer risk (per allele HR = 1.28, 95% CI 1.18-1.39, ). These results indicate that SNPs that modify BRCA2 penetrance identified by an agnostic approach thus far are limited to variants that also modify risk of sporadic BRCA2 wild-type breast cancer.     

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.     

A novel statin-mediated “prenylation block-and-release” assay provides insight into the membrane targeting mechanisms of small GTPases

Ras super-family small GTPases regulate diverse cellular processes such as vesicular transport and signal transduction. Critical to these activities is the ability of these proteins to target to specific intracellular membranes. To allow association with membranes Ras-related GTPases are post-translationally modified by covalent attachment of prenyl groups to conserved cysteine residues at or near their C-terminus. Here we used the HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase (HMGCR) inhibitor mevastatin to develop a ‘prenylation block-and-release’ assay that allows membrane targeting of prenylated proteins to be visualized in living cells. Using this assay we investigated the cytosol to membrane targeting of several small GTPases to compartments of the secretory and endocytic pathways. We found that all Rabs tested were targeted directly to the membrane on which they reside at steady-state and not via an intermediate location as reported for Ras and Rho proteins. However, we observed that the kinetics of cytosol to membrane targeting differed for each Rab tested. Comparison of the mevastatin sensitivity and kinetics of membrane targeting of Rab23, Rab23 prenylation motif mutants and H-Ras revealed that these parameters are strongly dependent upon the prenyl transferase with Rab geranylgeranyl transferase substrates exhibiting higher sensitivity and requiring greater time to recover from mevastatin inhibition than farnesyl transferase substrates. We propose that this assay is a useful tool to investigate the kinetics, biological functions and the mechanisms of membrane targeting of prenylated proteins.     

Characterization and multiplexing of EST-SSR primers in Cynodon (Poaceae) species1

? Premise of the study: Cynodon species are multiple-use grasses that display varying levels of adaptation to biotic and abiotic stress. Previously identified EST-SSR primers were characterized and multiplexed to assess the level of genetic diversity present within a collection of almost 1200 Cynodon accessions from across Australia. ? Methods and Results: Two multiplex reactions were developed comprising a total of 16 EST-SSR markers. All SSR markers amplified across different Cynodon species and different levels of ploidy. The number of alleles ranged from one to eight per locus and the total number of alleles for the germplasm collection was 79. ? Conclusions: The 16 markers show sufficient variation for the characterization of Cynodon core collections and analysis of population genetic diversity in Cynodon grasses.