Genetic variation and control of chloroplast pigment concentrations and related needle-level traits in Picea rubens, Picea mariana, and their hybrids: moisture and light environmental effects

Chlorophyll pigment concentrations and proportions, nitrogen (N), and needle morphology traits, are important components of growth and were examined in five hybrid index categories from controlled crosses of various crosstypes, ranging from pure black spruce (BS) [Picea mariana (Mill.) B.S.P.] to pure red spruce (RS) (Picea rubens Sarg.) grown under controlled light and water environments. Black spruce had on average 10% greater total chlorophyll concentration (CHL) than RS. Red spruce had proportionately less chlorophyll a:b and CHL:CAR (carotenoid) ratios than BS. Nitrogen (N) concentrations were 1.75 and 1.60% for BS and RS, respectively. Black spruce had the lowest carbon (C):N ratio (29.7) and RS had among the highest (32.3). Interestingly, there was no difference in specific needle area among hybrid indices. Most of the chlorophyll pigment, C and N traits followed an additive inheritance model, evidenced by a near-linear relationship from BS to RS across hybrid indices. However, for CHL, CAR, and CHL:CAR ratio, parental analysis showed significant male effects and non-significant female and male × female interaction effects. Black spruce males had 15.1 and 9.6% higher CHL and CAR, respectively, than hybrid or RS males, thus showing an underlying paternally inherited genetic control. Controlling for N differences, analysis of covariance (ANCOVA) showed that sun-grown seedlings had 22.2% or 300 μg g⁻¹ lower CHL than shade-grown seedlings. Controlling for N, ANCOVA showed that the drought-grown seedlings actually had 6.7% or 100 μg g⁻¹ greater CHL than the irrigated seedlings. Sun plus drought conditions gave the lowest CHL, N, and CHL:CAR ratio of all treatments, showing an additive multi-stress effect. There was a significant hybrid index × light effect as a result of rank changes. Sun-grown RS had the lowest CHL and N values, whereas shade-grown RS had among the highest CHL and N values. Red spruce are at a competitive disadvantage compared with BS and most hybrid spruce in high light, high drought, and high light plus drought conditions. Red spruce will be strongly limited in its distribution by successional opportunities resulting from prevalent harvesting practices such as clearcutting. Silvicultural modifications and genetic restoration will be required to maintain RS on the landscape of northeastern North America.     

Use of selection with recurrent backcrossing and QTL mapping to identify loci contributing to southern leaf blight resistance in a highly resistant maize line

B73 is a historically important maize line with excellent yield potential but high susceptibility to the foliar disease southern leaf blight (SLB). NC292 and NC330 are B73 near-isogenic lines (NILs) that are highly resistant to SLB. They were derived by repeated backcrossing of an elite source of SLB resistance (NC250P) to B73, with selection for SLB resistance among and within backcross families. The goal of this paper was to characterize the loci responsible for the increased SLB resistance of NC292 and NC330 and to determine how many of the SLB disease resistance quantitative trait loci (dQTL) were selected for in the development of NC292 and NC330. Genomic regions that differentiated NC292 and NC330 from B73 and which may contribute to NC292 and NC330s enhanced SLB resistance were identified. Ten NC250P-derived introgressions were identified in both the NC292 and NC330 genomes of which eight were shared between genomes. dQTL were mapped in two F_2:3 populations derived from lines very closely related to the original parents of NC292 and NC330—(B73rhm1 × NC250A and NC250A × B73). Nine SLB dQTL were mapped in the combined populations using combined SLB disease data over all locations (SLB AllLocs). Of these, four dQTL precisely colocalized with NC250P introgressions in bins 2.05–2.06, 3.03, 6.01, and 9.02 and three were identified near NC250P introgressions in bins 1.09, 5.05–5.06, and 10.03. Therefore the breeding program used to develop NC292 and NC330 was highly effective in selecting for multiple SLB resistance alleles. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Recent Advances in the Synthesis of Plasmonic Bimetallic Nanoparticles

The importance of plasmonic nanoparticles in sensor development, imaging, photodiagnostics, and optoelectronics has resulted in a strong interest toward the development of straightforward synthetic methods for their preparation. In this article, we review some of the most significant advances that have been made in the synthesis of plasmonic bimetallic nanoparticles. Approaches to control morphology, with an emphasis on reactions that produce uniform particles with well-defined sizes and shapes and in high yields, are described. In addition, several characterization techniques that have been employed to elucidate the morphology of the particles are illustrated.     

Structural messenger RNA contains cytokeratin polymerization and depolymerization signals

We have previously shown that VegT mRNA plays a structural (translation-independent) role in the organization of the cytokeratin cytoskeleton in Xenopus oocytes. The depletion of VegT mRNA causes the fragmentation of the cytokeratin network in the vegetal cortex of Xenopus oocytes. This effect can be rescued by the injection of synthetic VegT RNA into the oocyte. Here, we show that the structural function of VegT mRNA in Xenopus oocyte depends on its combinatory signals for the induction or facilitation and for the maintenance of the depolymerization vs. polymerization status of cytokeratin filaments and that the 300-nucleotide fragment of VegT RNA isolated from the context of the entire molecule induces and maintains the depolymerization of cytokeratin filaments when injected into Xenopus oocytes. A computational analysis of three homologous Xenopus VegT mRNAs has revealed the presence, within this 300-nucleotide region, of a conserved base-pairing (hairpin) configuration that might function in RNA/protein interactions.     

Computational identification of RNA functional determinants by three-dimensional quantitative structure–activity relationships

Anti-infection drugs target vital functions of infectious agents, including their ribosome and other essential non-coding RNAs. One of the reasons infectious agents become resistant to drugs is due to mutations that eliminate drug-binding affinity while maintaining vital elements. Identifying these elements is based on the determination of viable and lethal mutants and associated structures. However, determining the structure of enough mutants at high resolution is not always possible. Here, we introduce a new computational method, MC-3DQSAR, to determine the vital elements of target RNA structure from mutagenesis and available high-resolution data. We applied the method to further characterize the structural determinants of the bacterial 23S ribosomal RNA sarcin–ricin loop (SRL), as well as those of the lead-activated and hammerhead ribozymes. The method was accurate in confirming experimentally determined essential structural elements and predicting the viability of new SRL variants, which were either observed in bacteria or validated in bacterial growth assays. Our results indicate that MC-3DQSAR could be used systematically to evaluate the drug-target potentials of any RNA sites using current high-resolution structural data.     

Genetically diverse mice are novel and valuable models of age-associated susceptibility to <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis>

Background

Tuberculosis, the disease due to Mycobacterium tuberculosis, is an important cause of morbidity and mortality in the elderly. Use of mouse models may accelerate insight into the disease and tests of therapies since mice age thirty times faster than humans. However, the majority of TB research relies on inbred mouse strains, and these results might not extrapolate well to the genetically diverse human population. We report here the first tests of M. tuberculosis infection in genetically heterogeneous aging mice, testing if old mice benefit from rapamycin.

Findings

We find that genetically diverse aging mice are much more susceptible than young mice to M. tuberculosis, as are aging human beings. We also find that rapamycin boosts immune responses during primary infection but fails to increase survival.

Conclusions

Genetically diverse mouse models provide a valuable resource to study how age influences responses and susceptibility to pathogens and to test interventions. Additionally, surrogate markers such as immune measures may not predict whether interventions improve survival.