Cell competence forAgrobacterium-mediated DNA transfer inPisum sativum L.

Distribution and properties of pea (Pisum sativum L.) cells, competent forAgrobacterium-mediated transformation were analysed byin situ histochemical detection of GUS (-glucuronidase) activity, 4 d after inoculation with engineeredAgrobacterium tumefaciens. The vector system consisted of the hypervirulent disarmed strain EHA101 and the binary plasmid pIBGUS, carrying an intron-containing, 35S-promotor drivengusA (oruidA) gene and two selectable marker genes. Cells competent for transformation were mainly restricted to the dedifferentiating cells neighbouring the vascular system of cotyledon and epicotyl explants. A standardized assay was developed, allowing determination and quantification of factors influencing number and distribution of competent cells. In etiolated seedlings, competence for transformation decreased with the distance of the epicotyl explant from the shoot apex and was specifically induced by the exogenous application of auxins. Transient expression ofgusA afterAgrobacterium-mediated DNA transfer was dramatically reduced upon application of cell-cycle and DNA replication inhibitors aphidicolin, colchicine and nalidixic acid. GUS expression after direct DNA transfer of double-stranded plasmid DNA (via PEG into protoplasts or via particle bombardment of epicotyl segments) was independent of cell-division/DNA replication.A GUS-positive mutant of EHA101 was constructed to allowin situ analysis of attaching bacteria within the plant tissue. Attachment and invasion was inhibited by well-developed cuticula but was restored after chloroform treatment of the tissue surface. Moreover, no correlation was found between distribution of attaching bacteria and the pattern of transformation-competent cells.     

Batch culture of Candida utilis in a medium deprived of a phosphorous source

Summary Candida utilis var. major NRRL-Y-1084 was grown in a defined medium without a phosphorous (P) source. During the exponential phase, cells divided according to a specific growth rate of 0.32 h^-1, which is lower than the usual rate for a balanced medium (0.4–0.6 h^-1). The relative P content of the biomass decreased from 2.70% to 0.75% over a period of 6 h, including 2 h of cell division arrest. At the end of this period there was another interruption of cell division. After that, multiplication restarted at a considerably lower rate and it deviated slightly from the exponential pattern. The stationary phase began when biomass P content reached 0.4%–0.5%, slowly decreasing afterwards to 0.25–0.20%. Biomass synthesis was less affected than cell division by the relative decrease of endogenous P, the two processes differing partially in their kinetics. Cell lysis started shortly before the stationary phase and affected about 20% of the population by the end of the assay. RNA and P content of the resulting biomass were 2.4% and 0.25% respecitvely, P being mainly incorporated to RNA.The relationship of biomass production to glucose uptake was very low, probably because the marked P deficiency called for an increase in energy consumption for growth and specially for maintenance. Compared with yeasts grown in a balanced medium, 40% increase in glycogen was observed, whereas no mean changes in the content of cell wall carbohydrates (glucan and mannan) and that of true protein were found.Member of the Scientific Researcher's Career of the Consejo Nacional de Investigaciones Cientificas y Técnicas (CONICET). Agrentina     

Allozyme variability and phylogenetic relationships in the cultivated potato (Solanum tuberosum) and related species

Gene frequencies at 13 isozyme loci were determined in three South American taxa of cultivated potatoes [the diploid group (gp.) Stenotomum, the diploid subgroups (subgp.) Goniocalyx, and the tetraploid gp. Andigena ofS. tuberosum], in the diploid weed speciesS. sparsipilum, and in most of the main cultivars now raised in the Northern Hemisphere (the tetraploid gp. Tuberosum ofS. tuberosum). High levels of genetic variability (mean number of alleles per locus, percentage of polymorphic loci, and mean heterozygosity) were detected, being higher in tetraploid potatoes. An equilibrium among the evolutionary factors which increase genetic variability and artificial selection for maximum yield would explain the high uniformity of heterozygosity values we observed in both Andigena (0.36 ± 0.02) and Tuberosum (0.38 ± 0.01) cultivars.—The low value of genetic distance (D = 0.044) between Stenotomum and Goniocalyx does not support the status of species forS. goniocalyx.—In most isozyme loci, the electromorphs of gp. Andigena were a combination of those found in both gp. Stenotomum andS. sparsipilum, suggesting an amphidiploid origin of gp. Andigena from that two diploid taxa. The presence in Andigena of unique electromorphs, which were lacking in both gp. Stenotomum andS. sparsipilum, suggests that other diploid species could be also implied in the origin of tetraploid Andean potatoes. Furthermore, since Andigena were more related to Stenotomum (D = 0.052) than toS. sparsipilum (D = 0.241), the autopolyploidization of Stenotomum individuals and the subsequent hybridization with gp. Andigena may also have occurred. Thus, our study suggests a multiple origin (amphidiploidy, autoploidy, and hybridization at tetraploid level) of gp. Andigena.—Most of the electromorphs of gp. Tuberosum were also found in gp. Andigena; both the direct derivation of that group from the Andean tetraploid potatoes and the repeated introgression provided by breeding programmes could explain this result. However, the allele c of Pgm-B, present in 30 out of 76 Tuberosum cultivars from Northern Hemisphere as well as in 3 Chilean Tuberosum cultivars, lacks in the 258 Andigena genotypes sampled, suggesting that Chilean germplasm could have taken part in the origin of at least the 39% of the potato cultivars from Europe and North America analyzed here.—The distanceWagner procedure provides an estimate of a 30% of heterogeneity in the evolutionary divergence shown by different groups of cultivated potatoes. Diploid groups show a higher (22.5%) evolutionary rate than tetraploids, which can be attributed to both tetrasomic inheritance and facultative autofecundation that exists in Andigena and Tuberosum groups. Thus, artificial selection acting since 10000 years has not resulted in a higher rate of molecular evolution at the isozyme level in the tetraploids.     

B-cells of the synovial membrane. II. Differentiation during development of the synovial cavity in the mouse

Summary Study of pre- and postnatal development of the metatarsophalangeal joint of the mouse shows that the synovial cavity (SC) forms before any differentiation of the synovial mesenchyme. The primitive cleft results from degradation of a thin vascular mesenchymal layer in direct contact with the chondrogenic layers. Differentiation of the synovial membrane coincides with clarification of the SC (3rd to 6th day of postnatal life). When dilatation of the SC occurs (6th to 8th day), the two intimal cells types (A- and B-cells) are well identified. The B-cells already show typical features at day 6; their content of typical dense secretory vesicles is comparable to that of the adult B-cells at day 13. The specific secretory function of B-cells could be correlated with the particular structure of the intimal interstitial tissue and could account for the origin of some protein(s) of the synovial fluid.ERA 178 (Neuroendocrinologie Comparée) du CNRS et INSERM     

Summer dispersal and survival of juvenile Great Tits in southern Sweden

Summary Movements and survival of 506 first-brood Great Tit nestlings that fledged in mid-June in an oak wood in southern Sweden were studied by intensive trapping in that wood and in several neighbouring woods between 17 July and 10 September 1977. A total of 1177 captures of 508 individuals was made.Two periods of summer dispersal can be distinguished: the first period, one to one- and-one-half months after fledging, lasts longer in females and results in females moving farther away from their birthplace than males; and the second period in early September. There was no effect of brood-size, fledging date or size on dispersal movements. There is, however, a nest effect in that siblings tend to be more alike in the distance moved than non-siblings.The summer mortality rate is constant but high (13% per week). It is not affected by brood size or fledging date, but during the first month after fledging large individuals survive better than smaller ones. The summer mortality rate of dispersers (birds moving between woods) is not higher than that of non-dispersers.The results contradict two hypotheses proposed to explain when and how postfledging mortality occurs. The mortality rate is not higher during the first month after fledging, as Perrins' and Lack's hypothesis predicts. Since only 22% of the young are still alive at the beginning of September, autumn territorial behaviour cannot be the main factor causing juvenile losses, as proposed by Kluyver.There is some circumstantial evidence that Great Tits compete for food during the summer, and that food therefore could be in short supply, as suggested by Perrins.The observed differential dispersal of adults and young, and of male and female juveniles, may be the result of the dominance relationships in the family flock and later in the summer flocks, with subordinate individuals moving farthest.     

Xanthones et C-glucosides flavoniques du genre Gentiana (section Cyclostigma)

Xanthones with a uniform 1,3,7,8-oxidation pattern, the C-glycosides isoorientin and isovitexin, and in some cases mangiferin, were isolated from the aerial parts of G. nivalis, G. brachyphylla, G. favrati, G. rostani, G. utriculosa and G. schleicheri Kunz. The distribution of these compounds within the section Cyclostigma is given. Comparison of phenolic patterns in other sections of Gentiana is made.     

Effects of amphotericin B on the electrical properties ofNecturus gallbladder: Intracellular microelectrode studies

Summary Intracellular microelectrode techniques were employed to study the mechanism by which amphotericin B induces a transient mucosa-negative transepithelial potential (V _ms) in the gallbladder ofNecturus. When the tissue was incubated in standard Na-Ringer's solution, the antibiotic reduced the apical membrane potential by about 40 mV, and the basolateral membrane potential by about 35 mV whereas the transepithelial potential increased by about 5 mV. The electrical resistance of the apical membrane fell by 83%, and that of the basolateral membrane by 40%; the paracellular resistance remained unchanged. Circuit analysis indicated that the equivalent electromotive forces of the apical and basolateral membranes fell by 35 and 11 mV, respectively. Changes in potentials and resistances produced by ionic substitutions in the mucosal bathing medium showed that amphotericin B produces a nonselective increase in apical membrane small monovalent cation conductance (K, Na, Li). In the presence of Na-Ringer's on the mucosal side, this resulted in a reduction of the K permselectivity of the membrane, and thus in a fall of its equivalent emf. During short term exposure to amphotericin B,P _Na/P _Cl across the paracellular pathway did not change significantly, whereasP _K/P _Na doubled. These results indicate that V _ms is due to an increase of g_Na across the luminal membranes of the epithelial cells (Cremaschiet al., 1977,J. Membrane Biol. 34:55); the data do not support the alternative hypothesis (Rose & Nahrwold, 1976.J. Membrane Biol. 29:1) that V _ms results from a reduction in shuntP _Na/P _Cl acting in combination with a rheogenic basolateral Na pump.