Morphological Constraints of Shoot Demography of a Clonal Plant: Extra- and Intravaginal Tillers of Festuca rubra

Abstract Festuca rubra forms tillers in two different ways: extravaginally and intravaginally. Demography of these two tiller types was observed in seventeen selected tussocks of Festuca rubra s.s. over four growing seasons. Extravaginal tillers were bigger at birth and on the average produced twice as many daughter tillers per tiller. In general, the natality and mortality of extravaginal tillers were less regular than that of intravaginal tillers. Overall tillering rate per tiller was correlated with the density of the surrounding vegetation; mortality, natality and tiller life span were not. High density of the surrounding vegetation did not result in increased formation of extravaginal tillers. The proportion of the extravaginal tillers was not correlated with the density of the F. rubra tussocks. There is no evidence for foraging by extravaginal tillers, but they do act as founders of small clusters of tillers.     

Regional patterns of diversity and estimates of global insect species richness

The total number of insect species in the world is an important if elusive figure. We use a fresh approach to estimate global insect species richness, based on biogeographic patterns of diversity of well or better documented taxa. Estimates generated by various calculations, all variations on a theme, largely serve to substantiate suggestions that insect species are likely to number around 10 million or less.     

Solution properties ofEscherichia coli-expressed VH domain of anti-neuraminidase antibody NC41

The V_H domain of anti-influenza neuraminidase antibody NC41, with and without a C-terminal hydrophilic marker peptide (FLAG^TM), has been expressed in high yield (15–27 mg/L) inEscherichia coli. Both forms were secreted into the periplasm where they formed insoluble aggregates which were solubilized quantitatively with 2 M guanidine hydrochloride and purified to homogeneity by ion-exchange chromatography. The V_H-FLAG was composed of three isoforms (pI values of ～4.6, 4.9, and 5.3) and the V_H molecule was composed of two isoforms with pI values of 5.1 and 6.7; the difference between the V_H isoforms was shown to be due to cyclization of the N-terminal glutamine residue in the pI 5.1 isoform. At 20°C and concentrations of 5–10mg/ml the V_H domain dimerized in solution and then partly precipitated, resulting in the broadening of resonances in its¹H NMR spectrum. Reagents such as CHAPS,n-octylglucoside, and ethylene glycol, which presumably mask the exposed hydrophobic interface of the V_H molecule, prevented dimerization of the V_H and permitted good-quality NMR spectra on isotope-labeled protein to be obtained.     

Analytical results concerning linkage disequilibrium in models with genetic transformation and conjugation

Expressions are obtained for the expected levels of linkage disequilibrium under three different equilibrium neutral models that make different assumptions about how recombination takes place. A transformation model is considered in which exchange events involve only one locus at a time. Two conjugation models are considered one with a linear genome and one with a circular genome. In the conjugation models large blocks of genes can be transferred with each conjugation. Consistent with published simulation results, it is found that if the transformation rate per locus is more than twenty times the mutation rate per locus, then the levels of linkage disequilibrium are quite low. If the number of loci being sampled is greater than 10, conjugation with a circular genome can be considerably more effective than transformation in reducing linkage disequilibrium. When recombination rates are high, expected linkage disequilibrium is shown to be proportional to the inverse of the transformation rate (or conjugation rate.)     

Microbial Hydrocarbon Co-oxidation. III. Isolation and Characterization of an alpha, alpha'-Dimethyl-cis, cis-Muconic Acid-producing Strain of Nocardia corallina

A soil isolate identified as a strain of Nocardia corallina accumulated α, α′-dimethyl-cis, cis-muconic acid under co-oxidation conditions employing n-hexadecane for growth and p-xylene as the co-oxidizable substrate. N. corallina V-49 was postulated to have two pathways for the oxidation of p-xylene. One pathway proceeds throughp-benzyl alcohol, p-tolualdehyde, and p-toluic acid to 2, 3-dihydroxy-p-toluic acid, and the other pathway results in ortho ring cleavage of 3, 6-dimethylpyrocatechol and hence accumulation of α,α′-dimethyl-cis, cis-muconic acid.     

Microbial Hydrocarbon Co-oxidation: I. Oxidation of Mono- and Dicyclic Hydrocarbons by Soil Isolates of the Genus Nocardia

Nocardia cultures, isolated from soil by use of n-paraffins as the sole carbon source, have been shown to bring about significant oxidation of several methyl-substituted mono- and dicyclic aromatic hydrocarbons. Oxygen uptake by washed cell suspensions was not a reliable indicator of oxidation. Under co-oxidation conditions in shaken flasks, o- and p-xylenes were oxidized to their respective mono-aromatic acids, o-toluic and p-toluic acids. In addition, a new fermentation product, 2, 3-dihydroxy-p-toluic acid, was found in the p-xylene oxidation system. Of 10 methyl-substituted naphthalenes tested (1-methyl, 2-methyl, 1, 3-dimethyl, 1, 4-dimethyl, 1, 5-dimethyl, 1, 8-dimethyl, 1, 6-dimethyl, 2, 3-dimethyl, 2, 6-dimethyl, 2, 7-dimethyl), only those containing a methyl group in the β position were oxidized at this position to the mono acid.     

ANTIGEN-INDUCED CHANGES IN LYMPHOID CELL HISTONES : I. Thymus

An acute effect of antigens on the nuclear histones of mouse thymocytes was investigated by means of cytophotometric measurements of thymocytes stained with ammoniacal-silver (A-S) and with fast green (FG). In addition, the DNA content was measured in terms of Feulgen staining. In terms of such staining it appeared that nuclei of control thymocytes contain a greater amount of nuclear histones and a higher histone/DNA ratio than do renal cell nuclei from the same animal. Within 1 hour after the injection of antigen the thymocyte nuclei appear to lose approximately 32 per cent and 20 per cent, respectively, of A-S and FG stainable nuclear proteins, while the Feulgen staining remains unchanged. Since the renal cell nuclei show no antigen-induced change in histone staining, the histone staining and histone/DNA ratios were found to be similar in the thymocytes and renal cells of the antigen-injected mice. The antigen-induced loss of thymocyte histones was also found to be associated with a change in the color of the A-S staining, from yellowish brown to black. This and other findings suggest that thymocyte nuclei contain an antigen-labile, lysine-rich histone. The implication of these observations in regard to the phenomenon of immunological competence is discussed and the need for continued investigation indicated.     

Mapping of new quantitative trait loci for sudden death syndrome and soybean cyst nematode resistance in two soybean populations

Key message

Novel QTL conferring resistance to both the SDS and SCN was detected in two RIL populations. Dual resistant RILs could be used in breeding programs for developing resistant soybean cultivars.

Abstract

Soybean cultivars, susceptible to the fungus Fusarium virguliforme, which causes sudden death syndrome (SDS), and to the soybean cyst nematode (SCN) (Heterodera glycines), suffer yield losses valued over a billion dollars annually. Both pathogens may occur in the same production fields. Planting of cultivars genetically resistant to both pathogens is considered one of the most effective means to control the two pathogens. The objective of the study was to map quantitative trait loci (QTL) underlying SDS and SCN resistances. Two recombinant inbred line (RIL) populations were developed by crossing ‘A95-684043’, a high-yielding maturity group (MG) II line resistant to SCN, with ‘LS94-3207’ and ‘LS98-0582’ of MG IV, resistant to both F. virguliforme and SCN. Two hundred F₇ derived recombinant inbred lines from each population AX19286 (A95-684043 × LS94-3207) and AX19287 (A95-684043 × LS98-0582) were screened for resistance to each pathogen under greenhouse conditions. Five hundred and eighty and 371 SNP markers were used for mapping resistance QTL in each population. In AX19286, one novel SCN resistance QTL was mapped to chromosome 8. In AX19287, one novel SDS resistance QTL was mapped to chromosome 17 and one novel SCN resistance QTL was mapped to chromosome 11. Previously identified additional SDS and SCN resistance QTL were also detected in the study. Lines possessing superior resistance to both pathogens were also identified and could be used as germplasm sources for breeding SDS- and SCN-resistant soybean cultivars.