Optimizing purebred selection for crossbred performance using QTL with different degrees of dominance

A method was developed to optimize simultaneous selection for a quantitative trait with a known QTL within a male and a female line to maximize crossbred performance from a two-way cross. Strategies to maximize cumulative discounted response in crossbred performance over ten generations were derived by optimizing weights in an index of a QTL and phenotype. Strategies were compared to selection on purebred phenotype. Extra responses were limited for QTL with additive and partial dominance effects, but substantial for QTL with over-dominance, for which optimal QTL selection resulted in differential selection in male and female lines to increase the frequency of heterozygotes and polygenic responses. For over-dominant QTL, maximization of crossbred performance one generation at a time resulted in similar responses as optimization across all generations and simultaneous optimal selection in a male and female line resulted in greater response than optimal selection within a single line without crossbreeding. Results show that strategic use of information on over-dominant QTL can enhance crossbred performance without crossbred testing.     

Subsociality and female reproductive success in a mycophagous thrips: An observational and experimental analysis

Oviparous females of the haplodiploid, facultatively viviparous thrips Elaphrothrips tuberculatus(Thysanoptera: Phlaeothripidae) guard their eggs against female conspecifics and other egg predators. The intensity of maternal defense increases with clutch size. Field and laboratory observations indicate that cannibalism by females is an important selective pressure favoring maternal care. Experimental removals of guarding females showed that egg guarding substantially increases egg survivorship and that the survivorship of undefended eggs is higher in the absence of nonguarding female conspecifics than in their presence. The fecundity of viviparous females increases with the number of eggs cannibalized. The reproductive success of oviparous females increases with body size and local food density and decreases with local density of breeding females. Social behavior may not have advanced beyond maternal care in Elaphrothrips tuberculatusbecause, relative to Hymenoptera, capabilities for helping relatives are few or nonexistent, and the causes of variation in female reproductive success are not influenced easily by cooperation among females.     

Effect of postnatal development on calcium currents and slow charge movement in mammalian skeletal muscle

Single- (whole-cell patch) and two-electrode voltage-clamp techniques were used to measure transient (Ifast) and sustained (Islow) calcium currents, linear capacitance, and slow, voltage-dependent charge movements in freshly dissociated fibers of the flexor digitorum brevis (FDB) muscle of rats of various postnatal ages. Peak Ifast was largest in FDB fibers of neonatal (1-5 d) rats, having a magnitude in 10 mM external Ca of 1.4 +/- 0.9 pA/pF (mean +/- SD; current normalized by linear fiber capacitance). Peak Ifast was smaller in FDB fibers of older animals, and by approximately 3 wk postnatal, it was so small as to be unmeasurable. By contrast, the magnitudes of Islow and charge movement increased substantially during postnatal development. Peak Islow was 3.6 +/- 2.5 pA/pF in FDB fibers of 1-5-d rats and increased to 16.4 +/- 6.5 pA/pF in 45-50-d-old rats; for these same two age groups, Qmax, the total mobile charge measurable as charge movement, was 6.0 +/- 1.7 and 23.8 +/- 4.0 nC/microF, respectively. As both Islow and charge movement are thought to arise in the transverse-tubular system, linear capacitance normalized by the area of fiber surface was determined as an indirect measure of the membrane area of the t-system relative to that of the fiber surface. This parameter increased from 1.5 +/- 0.2 microF/cm2 in 2-d fibers to 2.9 +/- 0.4 microF/cm2 in 44-d fibers. The increases in peak Islow, Qmax, and normalized linear capacitance all had similar time courses. Although the function of Islow is unknown, the substantial postnatal increase in its magnitude suggests that it plays an important role in the physiology of skeletal muscle.     

Fasciation induction by the phytopathogen Rhodococcus fascians depends upon a linear plasmid encoding a cytokinin synthase gene.

Rhodococcus fascians is a nocardiform bacteria that induces leafy galls (fasciation) on dicotyledonous and several monocotyledonous plants. The wild-type strain D188 contained a conjugative, 200 kb linear extrachromosomal element, pFiD188. Linear plasmid-cured strains were avirulent and reintroduction of this linear element restored virulence. Pulsed field electrophoresis indicated that the chromosome might also be a linear molecule of 4 megabases. Three loci involved in phytopathogenicity have been identified by insertion mutagenesis of this Fi plasmid. Inactivation of the fas locus resulted in avirulent strains, whereas insertions in the two other loci affected the degree of virulence, yielding attenuated (att) and hypervirulent (hyp) bacteria. One of the genes within the fas locus encoded an isopentenyltranferase (IPT) with low homology to analogous proteins from Gram-negative phytopathogenic bacteria. IPT activity was detected after expression of this protein in Escherichia coli cells. In R.fascians, ipt expression could only be detected in bacteria induced with extracts from fasciated tissue. R.fascians strains without the linear plasmid but containing this fas locus alone could not provoke any phenotype on plants, indicating additional genes from the linear plasmid were also essential for virulence. These studies, the first genetic analysis of the interaction of a Gram-positive bacterium with plants, suggest that a novel mechanism for plant tumour induction has evolved in R.fascians independently from the other branches of the eubacteria.     

The fas operon of Rhodococcus fascians encodes new genes required for efficient fasciation of host plants.

Three virulence loci (fas, att, and hyp) of Rhodococcus fascians D188 have been identified on a 200-kb conjugative linear plasmid (pFiD188). The fas locus was delimited to a 6.5-kb DNA fragment by insertion mutagenesis, single homologous disruptive recombination, and in trans complementation of different avirulent insertion mutants. The locus is arranged as a large operon containing six open reading frames whose expression is specifically induced during the interaction with host plants. One predicted protein is homologous to P-450 cytochromes from actinomycetes. The putative ferredoxin component is of a novel type containing additional domains homologous to transketolases from chemoautotrophic, photosynthetic, and methylotrophic microorganisms. Genetic analysis revealed that fas encodes, in addition to the previously identified ipt, at least two new genes that are involved in fasciation development, one of which is only required on older tobacco plants.     

Three conditions for the evolution of eusociality: Are they sufficient?

Summary I hypothesize that three conditions, (1) food-shelter coincidence, (2) strong selection for defense, and (3) ability to defend, are sufficient, although not necessary, for the evolution of eusociality in group-living animals. Reasons for this association between ecology and eusociality include extremely high value of the habitat, possibilities for habitat inheritance, high relatedness in claustral situations, self-sufficiency of juveniles, greater ability of workers to reproduce, and trade-offs between defensive ability and dispersal.     

The location of retinal in the purple membrane profile by neutron diffraction.

The trans-membrane location of retinal in the purple membrane of Halobacterium halobium, has been determined by low-angle neutron scattering studies on aqueous dispersions of the membranes. The membrane was bleached and regenerated with deuterated and with hydrogen-containing retinal. The modified retinal was obtained by extraction from bacteria grown in a totally deuterated medium. The determination of the retinal position is based on the differences in neutron scattering between a purple membrane sample with normal, protonated retinal and another sample with deuterated retinal. A distinct scattering density difference between the two preparations was observed. A direct structure determination was used with the retinal localized from a Fourier difference density profile. We conclude that the β-ionone ring portion of the retinal is situated centrally in the membrane.     

Fructose as a carbohydrate source yields stable pH and redox parameters in microcarrier cell culture

The pH and cytosolic NADH/NAD⁺ redox potential in microcarrier cultures of Madin-Darby canine kidney cells remain within physiological range when fructose is substituted for glucose in medium formulation. This difference is accounted for by the low rate of lactic acid production in cultures utilizing fructose as a primary carbohydrate source.