The evolution of sexual size dimorphism in the house finch. V. Maternal effects

The phenotype of a mother and the environment that she provides might differentially affect the phenotypes of her sons and daughters, leading to change in sexual size dimorphism. Whereas these maternal effects should evolve to accommodate the adaptations of both the maternal and offspring generations, the mechanisms by which this is accomplished are rarely known. In birds, females adjust the onset of incubation (coincident with the first egg or after all eggs are laid) in response to the environment during breeding, and thus, indirectly, determine the duration of offspring growth. In the two house finch (Carpodacus mexicanus) populations that breed at the extremes of the species' distribution (Montana and Alabama), females experience highly distinct climatic conditions during nesting. We show that in close association with these conditions, females adjusted jointly the onset of incubation and the sequence in which they produced male and female eggs and consequently modified the growth of sons and daughters. The onset of incubation in newly breeding females closely tracked ambient temperature in a pattern consistent with the maintenance of egg viability. Because of the very different climates in Montana and Alabama, females in these populations showed the opposite patterns of seasonal change in incubation onset and the opposite sex bias in egg-laying order. In females with breeding experience, incubation onset and sex bias in laying order were closely linked regardless of the climatic variation. In nests in which incubation began with the onset of egg laying, the first-laid eggs were mostly females in Montana, but mostly males in Alabama. Because in both populations, male, but not female, embryos grew faster when exposed to longer incubation, the sex-bias produced highly divergent sizes of male and female juveniles between the populations. Overall, the compensatory interaction between the onset of incubation and the sex-biased laying order achieved a compromise between maternal and offspring adaptations and contributed to rapid morphological divergence in sexual dimorphism between populations of the house finch breeding at the climatic extremes of the species range.     

Genome sequence of Ensifer meliloti strain WSM1022; a highly effective microsymbiont of the model legume Medicago truncatula A17

Ensifer meliloti WSM1022 is an aerobic, motile, Gram-negative, non-spore-forming rod that can exist as a soil saprophyte or as a legume microsymbiont of Medicago. WSM1022 was isolated in 1987 from a nodule recovered from the roots of the annual Medicago orbicularis growing on the Cyclades Island of Naxos in Greece. WSM1022 is highly effective at fixing nitrogen with M. truncatula and other annual species such as M. tornata and M. littoralis and is also highly effective with the perennial M. sativa (alfalfa or lucerne). In common with other characterized E. meliloti strains, WSM1022 will nodulate but fixes poorly with M. polymorpha and M. sphaerocarpos and does not nodulate M. murex. Here we describe the features of E. meliloti WSM1022, together with genome sequence information and its annotation. The 6,649,661 bp high-quality-draft genome is arranged into 121 scaffolds of 125 contigs containing 6,323 protein-coding genes and 75 RNA-only encoding genes, and is one of 100 rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project.     

Using a targeted chemical nuclease to elucidate conformational changes in the E. coli 30S ribosomal subunit

Determining the detailed tertiary structure of 16S rRNA within 30S ribosomal subunits remains a challenging problem. The particular structure of the RNA which allows tRNA to effectively interact with the associated mRNA during protein synthesis remains particularly ambiguous. This study utilizes a chemical nuclease, 1, 10-o-phenanthroline-copper, to localize regions of 16S rRNA proximal to the decoding region under conditions in which tRNA does not readily associate with the 30S subunit (inactive conformation), and under conditions which optimize tRNA binding (active conformation). By covalently attaching 1,10-phenanthroline-copper to a DNA oligomer complementary to nucleotides in the decoding region (1396-1403), we have determined that nucleotides 923-929, 1391-1396, and 1190-1192 are within approximately 15 A of the nucleotide base-paired to nucleotide 1403 in inactive subunits, but in active subunits only cleavages (1404-1405) immediately proximal to the 5' end of the hybridized probe remain. These results provide evidence for dynamic movement in the 30S ribosomal subunit, reported for the first time using a targeted chemical nuclease.     

Prediction of F3 row performance from F2 individual plant data in oats

Summary Parameters estimated from a Gardner-Eberhart analysis of the F₂ generation of a six-parent diallel in oats (Avena sativa L.) were used to compare methods for predicting the performance of F₃ row plots. The prediction methods were: (1) individual F₂ plant performance (F2I), (2) parent average plus F₂ plot deviations (PF2), (3) parent average plus weighted F₂ plot deviations (PF2P), (4) best linear unbiased prediction (BLUP) of parent average plus F₂ plot deviations (BPF2), and (5) BLUP plus weighted F₂ deviations (BF2). The F₂ single-plant traits used for prediction were biological yield to predict F₃ biological yield, whole plant and primary tiller grain yield for prediction of F₃ grain yield, and whole plant and primary tiller harvest index (HI) to predict F₃ HI. Prediction methods were evaluated by correlations between predicted and observed F₃ performance. Prediction methods and traits for which correlations were greater than for F2I included: BF2 for biological yield, PF2, PF2P and BF2 for whole plant grain yield, PF2, BPF2, and BF2 for primary tiller grain yield. None had a correlation significantly greater than F2I for either measure of HI, where heritability was large. PF2 is the recommended method for traits with low heritability because of its simplicity and because it had the largest or nearly the largest correlation for each of the yield traits. F2I is the recommended method for traits with larger heritability.Contribution No. 8821 of the U.S. Regional Pasture Research LaboratoryDeceased     

Structural Insights into the Inhibition of Zika Virus NS2B-NS3 Protease by a Small-Molecule Inhibitor

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The kinetics of milk coagulation: IV. The kinetics of the gel-firming process

A mechanistic kinetic model of gel firmness development during milk gel formation is presented. The model correctly accounts for the influence of enzymatic kappa-casein hydrolysis on the rate of firmness development in renneted milk gels. The model used is based on two first-order reactions occurring in series. The first reaction is enzymatically controlled and corresponds to the formation of gel crosslink sites by kappa-casein hydrolysis. The second reaction is nonenzymatic and corresponds to the process of crosslink formation and depletion of active sites. The model successfully predicts gel firmness development in the temperature range 31-45 degrees C for a variety of initial enzyme concentrations.     

Selective inhibition of selenocysteine tRNA maturation and selenoprotein synthesis in transgenic mice expressing isopentenyladenosine-deficient selenocysteine tRNA

Selenocysteine (Sec) tRNA (tRNA([Ser]Sec)) serves as both the site of Sec biosynthesis and the adapter molecule for donation of this amino acid to protein. The consequences on selenoprotein biosynthesis of overexpressing either the wild type or a mutant tRNA([Ser]Sec) lacking the modified base, isopentenyladenosine, in its anticodon loop were examined by introducing multiple copies of the corresponding tRNA([Ser]Sec) genes into the mouse genome. Overexpression of wild-type tRNA([Ser]Sec) did not affect selenoprotein synthesis. In contrast, the levels of numerous selenoproteins decreased in mice expressing isopentenyladenosine-deficient (i(6)A(-)) tRNA([Ser]Sec) in a protein- and tissue-specific manner. Cytosolic glutathione peroxidase and mitochondrial thioredoxin reductase 3 were the most and least affected selenoproteins, while selenoprotein expression was most and least affected in the liver and testes, respectively. The defect in selenoprotein expression occurred at translation, since selenoprotein mRNA levels were largely unaffected. Analysis of the tRNA([Ser]Sec) population showed that expression of i(6)A(-) tRNA([Ser]Sec) altered the distribution of the two major isoforms, whereby the maturation of tRNA([Ser]Sec) by methylation of the nucleoside in the wobble position was repressed. The data suggest that the levels of i(6)A(-) tRNA([Ser]Sec) and wild-type tRNA([Ser]Sec) are regulated independently and that the amount of wild-type tRNA([Ser]Sec) is determined, at least in part, by a feedback mechanism governed by the level of the tRNA([Ser]Sec) population. This study marks the first example of transgenic mice engineered to contain functional tRNA transgenes and suggests that i(6)A(-) tRNA([Ser]Sec) transgenic mice will be useful in assessing the biological roles of selenoproteins.     

Developmental control of xylem hydraulic resistances and vulnerability to embolism in Fraxinus excelsior L.: impacts on water relations

The freezing tolerance of many plants, such as pea (Pisum sativum),is increased by exposure to low temperature or abscisic acidtreatment, although the physiological basis of this phenomenonis poorly understood. The freezing tolerance of pea shoot tips,root tips, and epicotyl tissue was tested after cold acclimationat 2C, dehydration/rehydration, applications of 10^–4M abscisic acid (ABA), and deacclimation at 25C. Tests wereconducted using the cultivar ‘Alaska’, an ABA-deficientmutant ‘wil’, and its ‘wildtype’. Freezinginjury was determined graphically as the temperature that caused50% injury (T₅₀) from electrical conductivity. Endogenous ABAwas measured using an indirect enzyme-linked immunosorbant assay,and novel proteins were detected using 2-dimensional polyacrylamidegel electrophoresis. The maximum decrease in T₅₀ for root tissuewas 1C for all genotypes, regardless of treatment. For ‘Alaska’shoot tips and epicotyl tissue, exogenous ABA increased thefreezing tolerance by –1.5 to –4.0C, while coldtreatment increased the freezing tolerance by –7.5 to–14.8C. Cold treatment increased the freezing toleranceof shoot tips by –9 and –15C for ‘wil’and ‘wild-type’, respectively. Cold acclimationincreased endogenous ABA concentrations in ‘Alaska’shoot tips and epicotyls 3- to 4-fold. Immunogold labeling increasednoticeably in the nucleus and cytoplasm of the epicotyl after7 d at 2C and was greatest after 30 d at the time of maximumfreezing tolerance and soluble ABA concentration. Cold treatmentinduced the production of seven, three, and two proteins inshoot, epicotyl, and root tissue of ‘Alaska’, respectively.In ‘Alaska’ shoot tissue, five out of seven novelproteins accumulated in response to both ABA and cold treatment.However, only a 24 kDa protein was produced in ‘wil’and ‘wild-type’ shoot and epicotyl tissues aftercold treatment. Abscisic acid and cold treatment additivelyincreased the freezing tolerance of pea epicotyl and shoot tissuesthrough apparently independent mechanisms that both resultedin the production of a 24 kDa protein. Key words: Pisum sativum, cold acclimation, immuno-localization