Triple test cross predictions of the performance of recombinant inbred lines from a wide cross in onions (Allium cepa)

In conjunction with an onion breeding scheme to produce recombinant inbred lines from a wide cross genetical experiments were carried out to predict the likely outcome. Results are given of genetical predictions, obtained from two triple test cross experiments, of the expected performance of inbred lines derivable by single seed descent from a Japanese × Polish cross. For bulb maturity, c. 12% of the inbred lines are expected to be earlier than the earlier parent; for bulb hardness over 50% of the inbred lines are expected to exceed the better parent. For bulb weight, predictions from the basic model suggest 5–25% of the inbred lines may exceed the better parent, but when this model is modified to take account of the likely inbreeding depression in the open-pollinated Japanese parent, only 0–2% of such high yielding inbred lines are expected. Other potential sources of bias which may affect the predictions are discussed.     

Establishment,Maintenance, and Integration Mechanisms of Endosymbionts in Protozoa1

ABSTRACT. Important progress has been made in recent years towards better understanding of the establishment and maintenance of endosymbiosis in protozoa and of the eventual integrative mechanisms involved. Still, many problems remain to be investigated more thoroughly. In this paper, while treating and reviewing the subject broadly, particular and more detailed attention is given to three selected systems: endonuclear symbiosis by Holospora bacteria in Paramecium; algal (Chlorella) relationships with the “green”Paramecium (P. bursaria) as host; and the rod-shaped bacteria found in the cytoplasm of Amoeba proteus. Data concerning the physiology of food vacuoles, membrane transport, photobehavior, recognition specificity, enzyme activity, and the like are presented and reviewed and discussed in light of the growing literature on the overall subject of “endocytobiology.” Emphasized is the complicated network of interactions between symbiotic partners and the importance of the development of integrative mechanisms in the evolution of the many intimate associations known at the cellular level today.     

Phytogenic biosynthesis and emission of methyl acetate

Acetylation of plant metabolites fundamentally changes their volatility, solubility and activity as semiochemicals. Here we present a new technique termed dynamic ¹³C‐pulse chasing to track the fate of C_1–3 carbon atoms of pyruvate into the biosynthesis and emission of methyl acetate (MA) and CO₂. ¹³C‐labelling of MA and CO₂ branch emissions respond within minutes to changes in ¹³C‐positionally labelled pyruvate solutions fed through the transpiration stream. Strong ¹³C‐labelling of MA emissions occurred only under pyruvate‐2‐¹³C and pyruvate‐2,3‐¹³C feeding, but not pyruvate‐1‐¹³C feeding. In contrast, strong ¹³CO₂ emissions were only observed under pyruvate‐1‐¹³C feeding. These results demonstrate that MA (and other volatile and non‐volatile metabolites) derive from the C_2,3 atoms of pyruvate while the C₁ atom undergoes decarboxylation. The latter is a non‐mitochondrial source of CO₂ in the light generally not considered in studies of CO₂ sources and sinks. Within a tropical rainforest mesocosm, we also observed atmospheric concentrations of MA up to 0.6 ppbv that tracked light and temperature conditions. Moreover, signals partially attributed to MA were observed in ambient air within and above a tropical rainforest in the Amazon. Our study highlights the potential importance of acetyl coenzyme A (CoA) biosynthesis as a source of acetate esters and CO₂ to the atmosphere.     

Phenotypic differentiation and phylogenetic signal of wing shape in western European biting midges,Culicoides spp., of the subgenus Avaritia

In the past decade biting midges of the subgenus Avaritia (Diptera: Ceratopogonidae) have been popular subjects of applied entomological studies in Europe owing to their implication as biological vectors in outbreaks of bluetongue and Schmallenberg viruses. This study uses a combination of cytochrome oxidase subunit I barcode sequencing and geometric morphometric analyses to investigate wing shape as a means to infer species identification within this subgenus. In addition the congruence of morphological data with different phylogenetic hypotheses is tested. Five different species of the subgenus Avaritia were considered in the study (C. obsoletus (Meigen); C. scoticus Kettle and Lawson; C. chiopterus (Meigen); C. dewulfi Goetghebuer and C. imicola (Kieffer)). The study demonstrated that over 90% of individuals could be separated correctly into species by their wing shape and that patterns of morphological differentiation derived from the geometric morphometric analyses were congruent with phylogenies generated from sequencing data. Morphological data produced are congruent with monophyly of the subgenus Avaritia and the exclusion of C. dewulfi from the group containing C. obsoletus, C. scoticus and C. chiopterus. The implications of these results and their importance in a wider context of integrating multiple data types to interpret both phylogeny and species characterization is discussed.     

Alpha-Mannosidase II Isoenzyme in the Peribacteroid Space of Glycine max Root Nodules

Kinnback, A., Mellor, R. B. and Werner, D. 1987. Alpha-mannosidaseII isoenzyme in the peribacteroid space of Glycine max rootnodules.—J. exp. Bot. 38: 1373–1377. Three isoenzymes of alpha-mannosidase from soybean tissue wereseparated by isoelectric focussing. The vacuomal isoenzymesI and II accounted typically for over 90% of the activity inextracts from roots whether or not they were infected with Bradyrhizobiumjaponicum, tissue culture and effective nodules. Ineffectivenodules, on the other hand, contained up to 62% of the typicallyextracellular located isoenzyme III. The compartment betweenthe symbiotic partners (the peribacteroid space) contained onlyisoenzyme II. The bearing of isoenzyme distribution upon modelsof peribacteroid membrane biogenesis is discussed. Key words: Aipha-mannosidase, Bradyrhizobium japonicum, Glycine max, membrane flow/recycling, peribacteroid space, symbiosis