摘要:

AbstractA large number of plastid localized proteins are post‐translationally imported as precursor proteins from the cytosol into the organelle. Recognition and translocation is accomplished by a subset of chloroplast envelope proteins, which were identified by different but complementary methods. Theouterenvelopeproteins OEP 86, OEP 75, OEP 70 (a heat shock cognate 70 homologue) and OEP 34 are clearly involved in the import event and can be isolated as one functionally active translocation unit. For three of these proteins cDNA clones have been very recently obtained, namely OEP 86, OEP 75 and OEP 34. OEP 86 seems to be a precursor protein receptor which could be regulated by GTP binding and ATP‐dependent phosphorylation‐dephosphorylation. OEP 75 is part of the translocation pore traversing the membrane in multiple β‐sheets. OEP 34 is tightly associated with OEP 75. It represents a new type of GTP‐binding protein which possesses endogenous GTPase activity. Multiple GTP binding and hydrolysis cycles as well as protein phosphorylation‐dephosphorylation events might, therefore, regulate the interaction of a precursor protein with the translocation machinery of the outer envelope, making it very distinct from the mitochondrial outer membrane system. Further proteins of the inner envelope membrane, namely IEP 97 and IEP 36, have been implied to function in the translocation event. These recent data allow not only identification of the players in the game but also speculation about mechanisms and regulation of t

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00495.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractEssential precursors of the cocoa‐specific aroma components are formed during fermentation of cocoa seeds in the tropics. During the past decades, indications have accumulated that these aroma precursors are derived from seed proteins by acid‐induced proteolysis. This has been recently corroborated byin vitrostudies on the formation of the aroma‐related components. It has been shown that the essential proteolysis products are derived from the vicilin‐class (7S) globulins of the cocoa seeds by the cooperative action of an endogenous aspartic endoprotease and a carboxype

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00496.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAllozyme variation at 14 loci was studied electrophoretically in 19 population samples ofQuercus cerris, Q. pubescens, Q. petraea, andQ. robur. Genetic variation, measured as mean heterozygosity, was found to be high within populations but low among populations. A significant deficit of heterozygotes was observed in most of the populations ofQ. pubescens, Q. petraea, andQ. robur. At the species level,Q. cerris(sect.Cerris) appears to be clearly separated from the rest (sect.Quercus).Q. pubescens, Q. petraea, andQ. roburform a cluster of closely‐related species. The degree of genetic differentiation among these species is low, i.e. in the range normally found among con‐specific populations. Nevertheless, allozyme data allow the elaboration of a dendrogram which is in reasonable accordance with the taxonomic classification, but also supports the importance of hybridization and introgression. This is also underlined by the fact that the allelic differentiation at theGot‐2locus corresponds with the phenotypic classification (petraea‐like, hybrids, androbur‐like) in samples from mixed po

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00497.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractImages of individual exine units from the tectum ofNuphar luteum(L.) Sm. pollen were made using atomic force microscopy. These units were recorded as being 120 to 160 nm wide. Exine‐units sectioned transversally were circular and had a central circular (core) zone 40 nm or more in diameter. Exine unit‐structures inNupharhave an outer (binder) substructure coiled around a core z

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00498.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe reproductive biology ofManettia luteo‐rubrawas studied in the coastal montane Atlantic rain forest of southeastern Brazil. This Rubiaceae is a perennial vine that flowers all the year round, but has a flowering peak during the dry season. It presents reciprocal herkogamy, thus the plants are morphologically distylous. The morphs occur in a 1:1 ratio, and pollen diameter and corolla length vary between short and long‐styled flowers.Manettia luteo‐rubradisplays typical heterostylous self‐incompatibility and sets almost no fruits from self‐ or intramorph pollinations. The flowers are tubular, red with yellow lobes, and odourless. Anthesis is asynchronous, and the flowers last about four days. Concentration of sugars in nectar is similar in both morphs, ca. 24%, this concentration being typical for hummingbird flowers. Three species of hummingbirds are the major pollinators of the flowers ofM. luteo‐rubraat the study site: the hermitsPhaethornis eurynomeandP. squalidus, and the trochilineThalurania glaucopis. Three species ofHeliconiusbutterflies act as minor pollinators. Both morphs ofM. luteo‐rubraexhibit natural fruit‐set of about 80%, this reproductive output being maintained throughout the year by the pollinators' constancy

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00499.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe activities of superoxide dismutase, ascorbate peroxidase, monodehydroascorbate radical reductase, and dehydroascorbate reductase and the contents of ascorbate, chlorophyll and soluble protein were determined in beech (Fagus sylvatica, L.) foliage over two or three seasons. Four important stages of leaf development were distinguished: resting buds, emerging, mature and senescent leaves. Foliar buds in spring, prior to the emergence of new leaves, contained a lower chlorophyll content but a higher protein content and higher activities of ascorbate peroxidase and monodehydroascorbate radical reductase than mature leaves in summer. By contrast, superoxide dismutase and glutathione reductase activities and ascorbate contents were higher in mature leaves than in swollen foliar buds. Dehydroascorbate reductase activity was low in all developmental stages. Resting buds in winter contained activities of superoxide dismutase, ascorbate peroxidase and monodehydroascorbate radical reductase that were similar to those found in mature leaves in summer, whereas the contents of total and reduced ascorbate were 6‐ and 20‐times lower, respectively, in buds than in mature leaves. The low foliar concentration of reduced ascorbate in resting buds, despite high monodehydroascorbate radical reductase activity, suggests that the regeneration of ascorbate might be limited by the availability of reductant. High antioxidative capacity was conferred by mature beech leaves and may be an important protection measure for coping with the large fluctuations in temperature and exposure to elevated ozone concentrations in sum

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00500.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSixteen isolates of the red alga,Bostrychia tenuissimaKing et Puttock, from New South Wales, Victoria and South Australia were cultured in the laboratory and analysed for low molecular weight carbohydrates using13C‐NMR and HPLC techniques. All populations south of 34 °S contain D‐sorbitol in combination with the heteroside digeneaside. The isolates north of 34° S lack digeneaside, but contain D‐sorbitol and, in addition, an isomeric form D‐dulcitol. Moreover, the13C‐NMR spectra showed an unknown metabolite which was only measured in combination with digeneaside. While in the strains south of 34 °S digeneaside and the unknown compound occur in small quantities and remained unchanged with increasing salinities (5–60 ppt), the relatively high D‐sorbitol contents strongly increased under hypersaline conditions. In the populations north of 34 °S both the concentrations of D‐sorbitol and D‐dulcitol increased with increasing salinity. These data demonstrate the important role of polyols in the osmotic acclimation ofB. tenuissima. The ecological and/or biological factors controlling this geographical pattern of metabolite content are not known. However, the different carbohydrate patterns withinB. tenuissimaare considered as indicators of the development of p

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00501.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe 5′ upstream DNA ofRbcSgenes fromBrassica napuscontains sequence elements that specifically interact with DNA‐binding proteins of the transcription apparatusin vitro. To clarify if these sequences are functionalin vivo, we have studied them in transient expression experiments. Fragments generated by successive deletions of the 5′ upstream regions of twoRbcSgenes were fused in frame to the β‐glucuronidase (gusA) reporter gene and GUS activity was monitored fluorometrically after polyethylene glycol (PEG)‐mediated DNA uptake in mesophyll protoplasts fromNicotiana tabacumSR1. The results indicate modular organization ofcis‐elements that together account for full promoter activity. Whereas the TATA‐box region alone resulted in basal expression levels, enhanced GUS activity was observed in the presence of additional further‐upstream sequences, including the G‐box and the Gs‐box. For maximal activity, the presence of a region containing the I‐box was required. In addition to these putative activating DNA regions, evidence was obtained for regions that negatively affected GUS activity and hence may conta

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00502.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSix stocks each of the basidiomycetesPleurotus ostreatusandP. pulmonariuswere checked for intraspecific polymorphism and inheritance of mitochondrial DNA (mtDNA). Polymorphisms were extensive in both species after digestion with the endonucleasesHaeIII andHind III, and they were stock‐specific with one exception. The range of mtDNA sizes was similar for both taxa, lying between approximately 56 kb and 70 kb forP. ostreatusand 60 kb and 78 kb forP. pulmonarius.The inheritance of mtDNA was uniparental throughout. In pairings of monokaryons exhibiting specific mtDNA types, only one parental mtDNA type was recovered in the resulting dikaryons; while the mitochondria of the donor mycelium spread out, the mitochondria of the recipient mycelium apparently are lost. Certain mtDNA types were more often inherited than others. By examining this dominance of mtDNA types one could establish parentage for both specie

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00503.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSporangiophores of the zygomycete fungusPhycomyces blakesleeanusare sensitive to near UV and blue light. The quantum effectiveness of yellow and red light is more than 6 orders of magnitude below that of near UV or blue light. Phototropism mutants with a defect in the genemadCare about 106times less sensitive to blue light than the wild type. These mutants respond, however, to yellow and red light when the long wavelength light is given simultaneously with actinic blue light. In the presence of yellow or red light the photogravitropic threshold ofmadCmutants is lowered about 100‐fold though the yellow and the red light alone are phototropically ineffective. A step‐up of the fluence rate of broad‐band red light (>600 nm) from 6 × 10−3to 6W m−2elicits, in mutant C 148madC, a transient deceleration of the growth rate. The growth rate of the wild type is not affected by the same treatment. The results are interpreted in terms of a red light absorbing intermediate of the blue light photoreceptor ofPhycomyces. The intermediate should be short‐lived in the wild type and should accumulate i

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1995.tb00504.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY