Mobility and control among nomadic shepherds: The case of theraikas. II

This paper analyzes the relationship between leaders and ordinary shepherds among the raikas—nomadic shepherds from western India. It uses a neo-institutional perspective to show how control over information is crucial if shepherds are to prevent their leader from misusing the extensive powers he possesses to make decisions on their behalf. Control over information is not, however, sufficient. The paper argues that shepherds must also possess the capacity to impose sanctions if their leader oversteps the bounds of delegated decision-making authority. The paper highlights the importance of politics and the divergent interests of the shepherds and their leaders. In so doing, it allows inquiry into a system of social interactions that is characterized by conflicting interests and the negotiation of conflict, but is often perceived as harmonious. At the same time, the investigation offers new insights into other social situations structured by principal-agent relationships.     

Reduced transmitter release conferred by mutations in theslowpoke-encoded Ca2+-activated K+ channel gene ofDrosophila

Potassium channels control the repolarization of nerve terminals and thus play important roles in the control of synaptic transmission. Here we describe the effects of mutations in theslowpoke gene, which is the structural gene for a calcium activated potassium channel, on transmitter release at the neuromuscular junction inDrosophila melanogaster. Surprisingly, we find that theslowpoke mutant exhibits reduced transmitter release compared to normal. Similarly, theslowpoke mutation significantly suppresses the increased transmitter release conferred either by a mutation inShaker or by application of 4-aminopyridine, which blocks theShaker-encoded potassium channel at theDrosophila nerve terminal. Furthermore, theslowpoke mutation suppresses the striking increase in transmitter release that occurs following application of 4-aminopyridine to theether a go-go mutant. This suppression is most likely the result of a reduction of Ca²⁺ influx into the nerve terminal in theslowpoke mutant. We hypothesize that the effects of theslowpoke mutation are indirect, perhaps resulting from increased Ca²⁺ channel inactivation, decreased Na⁺ or Ca²⁺ channel localization or gene expression, or by increases in the expression or activity of potassium channels distinct fromslowpoke.     

Genetic analysis of two tomato mutants affected in the regulation of iron metabolism

Iron is one of the most important micronutrients for plants. Like other organisms, plants have developed active mechanisms for the acquisition of sufficient iron from the soil. Nevertheless, very little is known about the genetic mechanisms that control the active uptake. In tomato, two spontaneously derived mutants are available, which are defective in key steps that control this process. The recessive mutationchloronerva (chln) affects a gene which controls the synthesis of the non-protein amino acid nicotianamine (NA), a key component in the iron physiology of plants. The root system of the recessive mutantfer is unable to induce any of the characteristic responses to iron deficiency and iron uptake is thus completely blocked. We present a characterization of the double mutant, showing that thefer gene is epistatic over thechln gene and thus very likely to be one of the major genetic elements controlling iron physiology in tomato. In order to gain access to these two genes at the molecular level, both mutants were precisely mapped onto the high density RFLP map of tomato. Thechln gene is located on chromosome 1 and thefer gene is on chromosome 6 of tomato. Using this high-resolution map, a chromosome walk has been started to isolate thefer gene by map-based cloning. The isolation of thefer gene will provide new insights into the molecular mechanisms of iron uptake control in plants.     

Further studies of the sieve-element plastids of theCaryophyllales includingBarbeuia,Corrigiola, Lyallia,Microtea, Sarcobatus,andTelephium

The sieve-element plastids of 69 species of theCaryophyllales were investigated by transmission electron microscopy. All contained the specific subtype-P3 plastids characterized by a peripheral ring of protein filaments. The presence or absence of an additional central protein crystal and their shape being either polygonal or globular as well as the average sizes of the sieve-element plastids are useful features in the characterization of some families.—Barbeuia contains sieve-element plastids that confirm its placement within thePhytolaccaceae. Lyallia differs fromHectorella by including small starch grains in their sieve-element plastids, which otherwise by their globular crystals negate a closer connection to theCaryophyllaceae. The lack of a central protein crystal in its form-P3fs plastids placesMicrotea best within theChenopodiaceae. Sarcobatus, a so far uncontested member of theChenopodiaceae, contains form-P3cf plastids, i.e., including a central crystal not found elsewhere in this family.Telephium andCorrigiola, shifted back and forth betweenMolluginaceae andCaryophyllaceae, have form-P3cf(s) plastids with a polygonal crystal which favor their placement within theCaryophyllaceae.     

CENTRORADIALIS/TERMINAL FLOWER 1 gene homolog is conserved inN. tabacum, a determinate inflorescence plant

A mutation in theCENTRORADIALIS (CEN) gene ofAntirrhinum and in theTERMINAL FLOWER 1 (TFL1) gene ofArabidopsis causes their indeterminate inflorescence to determinate. We clonedCEN/TFL1 homologs fromNicotiana tabacum, the wild-type of which has a determinate inflorescence. TheCEN gene was expressed in the inflorescnece meristem and kept its inflorescence meristem identity, whereas the tobacco homolog (NCH) was expressed at a low level throughout the plant’s development. AlthoughCEN andNCH are highly homologous genes, they may have been recruited to different developmental functions during their evolution. TwoNCH genes are derived from amphidiploidN. tabacum, but both of them hybridized with its diploid parents,N. sylvestris andN. tomentosiformis. Southern blotting, and the genomic organization ofTFL1 inArabidopsis revealed that anotherCEN homolog exists in the genome ofArabidopsis. These results suggest that there are two copies of theCEN homolog per diploid plant. The extended abstract of a paper presented at the 13th International Symposium in Conjugation with Award of the International Prize for Biology “Frontier of Plant Biology” These two authors contributed to this work equally.     

Ducellieria chodati — Alge oder Pilz?

Ducellieria chodati Teiling is an organism rarely mentioned from plankton samples. Its propagation was unknown, and all earlier authors have failed to see that it is a colourless organism. Because of its structure and some chemical reactions,Ducellieria was thought to be a member of theXanthophyceae. Many living coenobia ofD. chodati from several Austrian lakes and some steps of their reproduction have been studied: Zoospores with two unequal flagella are released. After a mobile phase they settle on coniferous pollen grains drifting in water. Inside the pollen grain, a tube or flask is developed from which zoospores are released again after one or two days. These aggregate to form newDucellieria coenobia. These observations suggest thatDucellieria chodati belongs to thePhycomycetes, perhaps to theSaprolegniales.

     

Thealdox-2 locus ofDrosophila melanogaster also affects sulfite oxidase and molybdenum metabolism

Mutation at thealdox-2 locus inDrosophila melanogaster affects the specific activities of four molybdoenzymes differentially during development. Sulfite oxidase activity is normal during late larval and pupal stages but is reduced during early adult stages inaldox-2 organisms. There was complete concordance among the effects ofaldox-2 on sulfite oxidase, aldehyde oxidase, xanthine dehydrogenase, and pyridoxal oxidase, when 38 stocks were analyzed which were derived from single recombination events betweenc andpx, markers which flankaldox-2. Several different biochemical analyses indicate that the active molybdoenzymes present in thealdox-2 strain are normal with respect to size, shape,pH-activity profile,K _m , and molecular weight. Significant differences were found between thealdox-2 strain and the OR control strain in their responses to dietary Na₂MoO₄ and Na₂WO₄. The mutant strain is much more resistant to the effects of dietary Na₂WO₄ and much more responsive to the administration of Na₂MoO₄ than the OR control strain when these effects are quantitated by measurements of molybdoenzyme specific activities. This evidence suggests that thealdox-2 ⁺ gene product has a molybdenum binding site which can also bind tungsten and that this site is altered in the mutant strain. The hypothesis presented explains the observed effects of thealdox-2 mutation and relates them to the other mutations reported in this gene-enzyme system.This work was supported by an Operating Grant from the Natural Sciences and Engineering Research Council to M.M.B.     

Phylogenetic relationships of theJuglandaceae

A cladistic analysis of molecular data from the chloroplast generbcL was used to examine the taxonomic relationships of the walnut family (Juglandaceae). In addition, chemical and morphological data from a previous study byHufford (1992) were incorporated, expanded, and analyzed independently and in combination with the molecular data. The results of these analyses suggest that theJuglandaceae are more closely related to theFagaceae, Betulaceae, Casuarinaceae, andUrticaceae and their relatives (sensuCronquist 1981) than they are to theAnacardiaceae (sensuThorne 1983). However, sequence data fromrbcL also suggest a relationship between the higherHamamelidae and certain families in theRosidae sensuCronquist 1981 (such asRosaceae andRhamnaceae), an outcome which would add credence to the widely accepted view of the polyphyletic nature of theHamamelidae.     

Cloning of the cDNA and genomic clones for glutathione synthetase fromArabidopsis thaliana and complementation of agsh2 mutant in fission yeast

Glutathione is essential for protecting plants from a range of environmental stresses, including heavy metals where it acts as a precursor for the synthesis of phytochelatins. A 1658 bp cDNA clone for glutathione synthetase (gsh2) was isolated fromArabidopsis thaliana plants that were actively synthesizing glutathione upon exposure to cadmium. The sequence of the clone revealed a protein with an estimated molecular mass of 53858 Da that was very similar to the protein from higher eukaryotes, was less similar to the gene from the fission yeast,Schizosaccharomyces pombe, and shared only a small region of similarity with theEscherichia coli protein. A 4.3 kbSstI fragment containing the genomic clone for glutathione synthetase was also isolated and sequenced. A comparison of the cDNA and genomic sequences revealed that the gene was composed of twelve exons.When theArabidopsis cDNA cloned in a special shuttle vector was expressed in aS. pombe mutant deficient in glutathione synthetase activity, the plant cDNA was able to complement the yeast mutation. Glutathione synthetase activity was measurable in wild-type yeast cells, below detectable levels in thegsh2 ^- mutant, and restored to substantial levels by the expression of theArabidopsis cDNA. TheS. pombe mutant expressing the plant cDNA had near wild type levels of total cellular thiols,¹⁰⁹Cd²⁺ binding activity, and cadmium resistance. Since theArabidopsis cDNA was under control of a thiamine-repressible promoter, growth of the transformed yeast on thiamine-free medium increased expression of the cDNA resulting in increases in cadmium resistance.     

Seed coat structure ofCrocus vernus agg. (Iridaceae)

Cytotypes of theCrocus vernus aggregate differ slightly in their seed surface patterns.Crocus albiflorus may be grouped together withCrocus vernus subsp.vernus, both are relatively easily distinguishable by their seed surface patterns from theCrocus scepusiensis—Crocus heuffelianus group.     

Indirect evidence of alteration in the expression of the rDNA genes in interspecific hybrids betweenDrosophila melanogaster andDrosophila simulans

Crosses betweenDrosophila melanogaster females andD. simulans males produce viable hybrid females, while males are lethal. These males are rescued if they carry theD. simulans Lhr gene. This paper reports that females of the wild-typeD. melanogaster population Staket do not produce viable hybrid males when crossed withD. simulans Lhr males, a phenomenon which we designate as the Staket phenotype. The agent responsible for this phenomenon was found to be the StaketX chromosome (X ^mel ,Stk). Analysis of the Staket phenotype showed that it is suppressed by extra copies ofD. melanogaster rDNA genes and that theX ^mel ,Stk chromosome manifests a weak bobbed phenotype inD. melanogaster X ^mel ,Stk/0 males. The numbers of functional rDNA genes inX ^mel ,Stk andX ^mel ,y w (control) chromosomes were found not to differ significantly. Thus a reduction in rDNA gene number cannot account for the weak bobbedX ^mel ,Stk phenotype let alone the Staket phenotype. The rRNA precursor molecules transcribed from theX ^mel ,Stk rDNA genes seem to be correctly processed in both intraspecific (melanogaster) and interspecific (melanogaster-simulans) conditions. It is therefore suggested that theX ^mel ,Stk rDNA genes are inefficiently transcribed in themelanogaster-simulans hybrids.     

Lignin-degrading ability of litter-decomposing basidiomycetes fromPicea forests of Hokkaido

The frequency of occurrence of the litter-decomposing basidiomycetes ofPicea abies andP. glehnii forest floors in Hokkaido was investigated. In both theP. abies andP. glehnii forest plots (each 10 m×10 m), litter-decomposing basidiomycetes of the generaCollybia andMycena were frequently observed. Species composition, frequency of occurrence, and basidioma numbers of each species were different between the two forest plots, but several species were common to both. Seven species isolated from theP. glehnii forest plot (C. acervata, C. pinastris, Marasmius pallidocephalus, Ma. wettsteinii, My. aurantiidisca, My. clavicularis, Mycena sp. 1) and four species from theP. abies forest plot (C. pinastris, My. alphitophora (=My. osmundicola), Mycena sp. 1,My. vulgaris) were tested for their ability to degrade lignin by a simple plate test for extracellular phenoloxidases and by measuring Klason lignin loss from needle litter of spruce. All the strains of the litter-decomposing fungi tested showed positive reactions on the plate test. Lignin contained in the needle litter was degraded by all strains tested (onlyMy. alphitophora was not tested), and rates varied from 9% to 40% over a two-month period in vitro. Seven species with ligninolytic ability in theP. glehnii forest plot and four such species in theP. abies forest plot were found respectively in 77% and 60% of the 100 subplots in each plot. The results of this study suggest that lignin decomposition of needle litter by litter-decomposing basidiomycetes in the forest floor is a common event in the studiedPicea forests of Hokkaido and that the diversity of the ligninolytic activity among the species or strains may cause spatial heterogeneity of litter decomposition in thePicea forest floor.     

The fine structure of motile cells in the generaUlvaria andMonostroma,with special reference to the taxonomic position ofMonostroma oxyspermum (Ulvophyceae,Chlorophyta)

The zoospores and isogametes ofUlvaria obscura var.blyttii, the isogametes ofMonostroma bullosum, and the anisogametes ofM. grevillei have a flagellar apparatus with counterclockwise absolute orientation and terminal caps, and therefore belong to theUlvophyceae. On the basis of the absence or presence of body scales and the morphologies of certain flagellar apparatus components,Ulvaria obscura var.blyttii is retained in theUlvales, whileM. bullosum, M. grevillei andM. oxyspermum are referred to theUlotrichales. Differences in scale morphology, certain flagellar apparatus components, and early thallus ontogeny support the transfer ofM. oxyspermum to the genusGayralia. Mating structures and their positional relationships within the cell are described from the gametes examined. A plasmalemma-associated plaque that may be a degenerate mating structure occurs in someG. oxysperma motile cells.     

Sequence variation at theSec-1 locus of rye,Secale cereale (Poaceae)

This paper describes the structure of a 9.2-kb repeat unit of DNA, which represents one-secalin gene and spacer sequence located at theSec-1 locus on the short arm of chromosome 1 of rye. The gene units at theSec-1 locus comprise 1.1 kb representing the gene and 8.1 kb of spacer sequence separating the genes. A sequence comparison of nine genes and their promoter regions from theSec-1 locus, reveals that there is greater variation within the coding sequence than there is within the promoter regions. The gene sequence variation is discussed in terms of the size variation seen for the-secalin proteins in rye species. The results include a comparison of promoter sequences from members of the Triticeae to examine the degree of conservation between other seed storage protein genes.     

Über die Abgrenzung derChlorosarcinales von denChlorococcales

It is proposed to use amongst other characters the type of cell division in order to delimit theChlorosarcinales from theChlorococcales. A definition of the two processes of division occuring in these orders is given. It differs from that of other authors. In theChlorosarcinales only those genera should be assembled in which vegetative daughter cells arise by bipartition followed by firm association of the wall between the daughter cells with that of the mother cell. In contrast, autospores, the vegetative daughter cells of a number ofChlorococcales, develop by multiple division, their cell walls are formed all around the protoplasts and are free from that of the mother cell. The chlorococcalean generaTrebouxia andDictyochloropsis incorporate species which multiply by zoo-, aplano- and autospores as well as others having no autospores. Autospores possibly have arisen more than once during evolution.

     

Phylogenetic analysis ofUlmaceae

A phylogenetic analysis of theUlmaceae, Cannabaceae, Barbeyaceae, andBroussonetia of theMoraceae produced nine equally parsimonious trees with 127 steps. TheUlmoideae (Ulmaceae, sensuGrudzinskaya) are a monophyletic group and distinct from theCeltidoideae. The genusAmpelocera occupies an isolated taxonomic position among the celtidoids. The similarity ofAmpelocera to the fossil celtidoid flowerEoceltis of North America suggests thatAmpelocera posesses an archaic suite of characters, and occupies a primitive position among the celtidoids, theCannabaceae and theMoraceae. The relationships among the other celtidoid taxa,Cannabaceae, andBroussonetia are problematic. TheCannabaceae andBroussonetia of theMoraceae are nested within the celtidoids suggesting that this is a paraphyletic group. The close, but unresolved, relationship of the celtidoids to theMoraceae andCannabaceae observed in this analysis, and the appearance of the celtidoids in the fossil record prior to the ulmoids suggests that the evolutionary relationship of the ulmoids and celtidoids may be more distant than current taxonomic treatments reflect.     

TheSfm system of gene control inAntirrhinum majus

InAntirrhinum majus,pal-rec, an allele of thepallida series, is considered to be involved in anthocyanin production. Thepal-rec gene normally mutates autonomously from the recessive condition to the dominant giving fully pigmentedPal spots on a colorless background. TheSfm element, when inserted at thepal locus, destabilizes the activity of thepal-rec gene in such a way that the repressor (Sf) component abolishes gene activity in almost all of the cell lineages, whereas the mutator (m) acts to release full gene expression in some of the cells. Such a flip-flop control of thepal-rec results in what is known as shifting.     

The PSO4 gene is responsible for an error-prone recombinational DNA repair pathway in Saccharomyces cerevisiae

Summary The induction of mitotic gene conversion and crossing-over inSaccharomyces cerevisiae diploid cells homozygous for thepso4-1 mutation was examined in comparison to the corresponding wild-type strain. Thepso4-1 mutant strain was found to be completely blocked in mitotic recombination induced by photoaddition of mono- and bifunctional psoralen derivatives as well as by mono- (HN1) and bifunctional (HN2) nitrogen mustards or 254 nm UV radiation in both stationary and exponential phases of growth. Concerning the lethal effect, diploids homozygous for thepso4-1 mutation are more sensitive to all agents tested in any growth phase. However, this effect is more pronounced in the G2 phase of the cell cycle. These results imply that the ploidy effect and the resistance of budding cells are under the control of thePSO4 gene. On the other hand, thepso4-1 mutant is mutationally defective for all agents used. Therefore, thepso4-1 mutant has a generalized block in both recombination and mutation ability. This indicates that thePSO4 gene is involved in an error-prone repair pathway which relies on a recombinational mechanism, strongly suggesting an analogy between thepso4-1 mutation and theRecA orLexA mutation ofEscherichia coli.     

Regulation of nodulin gene expression

The expression of plant genes specifically induced during rhizobial infection and the early stages of nodule ontogeny (early nodulin genes) and those induced in the mature, nitrogen-fixing nodule (late nodulin genes) is differentially regulated and tissue/cell specific. We have been interested in the signal transduction pathway responsible for symbiotic, temporal and spatial control of expression of an early (Enod2) and a late (Leghemoglobin;lb) nodulin gene from the stem-nodulated legumeSesbania rostrata, and in identifying thecis-acting elements andtrans-acting factors involved in this process (De Bruijn and Schell, 1992). By introducing chimericS. rostrata lb promoter-gus reporter gene fusions into transgenicLotus corniculatus plants, we have been able to show that thelb promoter directs an infected-cell-specific expression pattern inLotus nodules. We have been able to delimit thecis-acting element responsible for nodule-infected-cell-expression to a 78 pb region of thelb promoter (NICE Element) and have analyzed this element in detail by site-specific mutagenesis. We have studied the interaction of the NICE element, and further upstreamcis-acting elements, withtrans-acting factors of both plant- and rhizobial origin. We have obtained evidence for the involvement of rhizobial proteins in infected-cell-specific plant gene expression (Welters et al., 1993). We have purified one of the bacterial binding proteins from theS. rostrata symbiontAzorhizobium caulinodans (AcBBP1), and cloned and mutated the corresponding gene, in order to examine its symbiotic phenotype. We have also found that theS. rostrata Enod2 gene is rapidly induced by physiologically significant concentrations of cytokinins, suggesting the role of cytokinin as a potential secondary signal involved in nodulation (Dehio and De Bruijn, 1992). We are examining whether the observed cytokinin induction, as well as the nodule-specific expression pattern, are modulated by theSrEnod2 promoter.