Sequential Analysis of the Organogenesis of Lucerne (Medicago sativa) Root Nodules Using Symbiotically-Defective Mutants of Rhizobium meliloti

Legume root-nodules are differentiated organs composed of peripheral tissue containing vascular bundles, and a central tissue in which are located the nitrogen-fixing bacteroids. The morphogenesis of these eukaryotic organs is induced by a prokaryotic organism, Rhizobium , which is amenable to genetic analysis. Inoculation of lucerne seedlings with leucine-requiring (Leu⁻) mutants of R. meliloti resulted in the formation of ineffective nodules. In these nodules, bacteria were not released from the infection threads into the host cytoplasm. When urea was provided as a nitrogen source to compensate for the defect in nitrogen fixation, the nodules became anatomically similar to those of effective nodules induced by the wild-type strain. The fact that these nodules were induced by bacteria which remained sequestered in infection threads indicates that nodule morphogenesis can be triggered from a distance. We hypothesize the existence of a bacterial nodule organogenesis-inducing principle (NOIP) which can cross the plant cell wall and plasmalemma.
In nitrogen-fixing nodules the central tissue exhibited a ploidy gradient, while in ineffective Leu⁻ nodules it was found to be monosomatic. The initiation of nodule formation is therefore independent of polyploidy. Supplying the defective plant-bacterial system with l -leucine or one of its precursors, α-ketoisovalerate or α-ketoisocaproate, caused the release of rhizobia into the plant cytoplasm and a restoration of nitrogen fixation. In the central tissue infected cells were polyploid and enlarged, and uninfected cells remained small and contained small nuclei. Therefore induction of differentiation of the central tissue requires the presence of bacteria in the cytoplasm. We hypothesize the role of a bacterial central tissue differentiation inducing principle (CTDIP) which cannot pass from cell to cell.     

Discotricha papillifera, n.g., n.sp. Cilié psammobie de la Famille des Trichopelmidae

A new sand-dwelling ciliate, Discotricha papillifera n.g., n.sp., is described and allocated to the trichostome family Trichopelmidae. The species seems to be one of the most highly differentiated members of the family. The peculiar type of its body ciliature and of its buccal structures suggests affinities with certain other major groups of ciliated protozoa; from an evolutionary point of view the organism appears to show close relationship to the gymnostome family Chlamydodontidae.     

A comparative study of sex pheromone reception in the Hadeninae (Lepidoptera: Noctuidae)

Abstract A comparative study of the olfactory responses to pheromone compounds was performed in twenty-four species of Hadeninae. Electroantennograms (EAG) were recorded on male moths in response to thirty compounds and the response profiles of each species were analysed by factorial correspondence analysis. A limited number of molecules were found active and the most effective stimuli were Z9 tetradecenes and Z11 hexadecenes. The species of the Mythimna genus were most sensitive to aldehydes. Tholera decimalis did not respond to any of the molecules tested. The species belonging to the Mamestra and the Orthosia genera responded to a variety of molecules and no simple correlation was found between the genus and the EAG sensibility. Pheromone reception is discussed in relation to the taxonomy and the evolution of olfactory communication in Hadeninae.     

Adipokinetic hormone of the true armyworm, Pseudaletia unipuncta: immunohistochemistry, amino acid analysis, quantification and bioassay

Abstract A cluster of five to seven AKH-like immunoreactive cells lie in each lobe of the paired corpora cardiaca of the true armyworm, Pseudaletia unipuncta. These cells form a mesh work of immunoreactive processes within the corpora cardiaca, and immunoreactive tracts projecting posteriorly over the aorta.
Reversed-phase high performance liquid chromatography of extracts of the corpora cardiaca of P.unipuncta revealed a single large U.V. absorbent peak with a retention time identical to synthetic Manduca- AKH. Amino acid analysis of the contents of this peak yielded a composition identical to that of synthetic Manduca-AKH which was analysed in a parallel manner. Furthermore the material within the peak possessed adipokinetic activity when bioassayed in day 2 adult male P. unipuncta. The corpora cardiaca of similar individuals were found to contain approximately 17.6ng (17.6pmol) of Manduca-AKH equivalents per pair.
Injection of Manduca-AKH into 2-day-old adult male P.unipuncta resulted in a dose-dependent elevation in haemolymph lipid levels with a maximum level of 80–90μmg/μl obtained with 5–10 ng of Manduca-AKH. Continuous flight also elevated haemolymph lipid levels in day 4 adult males with a significant elevation evident in the first samples taken after 15 min of flight and lipid levels plateauing at approximately 100 μg/μl by about 60 min of flight.     

GROWTH AND DEMOGRAPHY OF POPULATIONS OF BIOMPHALARIA PFEIFFERI (GASTROPODA, PLANORBIDAE) IN THE LABORATORY

The growth and demography of the freshwater snail Biomphalariapfeifferi, an intermediate host of the parasitic worm Schistosomamansoni in Eastern Zaire, were investigated in the laboratoryunder two conditions of crowding. Both individual and populationgrowth were depressed by crowding. Crowding reduced growth rateand all the variables and parameters related to reproduction(fecundity, instantaneous birth rate, net reproduction rate),but did not affect maximum size, survivorship, instantaneousdeath rate and life expectancy. The mechanism involved in theseeffects is likely to be exploitation competition for especiallyprofitable food items such as diatoms. (Received 10 November 1986;     

Identification and functional characterization of the Arabidopsis Snf1‐related protein kinase SnRK2.4 phosphatidic acid‐binding domain

Phosphatidic acid (PA) is an important signalling lipid involved in various stress‐induced signalling cascades. Two SnRK2 protein kinases (SnRK2.4 and SnRK2.10), previously identified as PA‐binding proteins, are shown here to prefer binding to PA over other anionic phospholipids and to associate with cellular membranes in response to salt stress in Arabidopsis roots. A 42 amino acid sequence was identified as the primary PA‐binding domain (PABD) of SnRK2.4. Unlike the full‐length SnRK2.4, neither the PABD‐YFP fusion protein nor the SnRK2.10 re‐localized into punctate structures upon salt stress treatment, showing that additional domains of the SnRK2.4 protein are required for its re‐localization during salt stress. Within the PABD, five basic amino acids, conserved in class 1 SnRK2s, were found to be necessary for PA binding. Remarkably, plants overexpressing the PABD, but not a non‐PA‐binding mutant version, showed a severe reduction in root growth. Together, this study biochemically characterizes the PA–SnRK2.4 interaction and shows that functionality of the SnRK2.4 PABD affects root development.