Structure of the dnaA region of the endosymbiont, Buchnera aphidicola, of aphid Schizaphis graminum

Buchnera aphidicola is an intracellular prokaryote (endosymbiont)that lives in the body cavity of the aphid. Phylogenetic studiesindicated that it is closely related to Escherichia coli andmembers of Enterobacteria. The gene order of the region containingthe dnaA gene is well conserved in many bacteria. Seven genesof the endosymbiont of the aphid Schizaphis graminum, gyrB,dnaN, dnaA, rpmH, rnpA, yidD, and 60K, were found to be homologousin sequence and relative location to those of E. coli. We havefurther sequenced the region downstream of the 60K gene to elucidatethe boundary of the conserved region, and found that one moregene, thdF , is conserved. The comparison of gene organizationsof the dnaA region of the related bacteria supported the closephylogenetic relationship of B. aphidicola to E. coli. In addition,we have identified groES and groEL genesnext to the thdF gene.GroEL protein was reported to be expressed at an elevated levelin the endosymbionts of aphids, and is considered to play animportant role in their association with the aphid host. Comparisonof the structure of the groE operon with that of the endosymbiontof the aphid Acyrthosiphon pisum revealed the conservation ofa sequence resembling the E. coli consensus heat shock promoter,and this sequence may be responsible for the high expressionof the groEL gene in aphid endosymbionts.     

The GUS reporter-aided analysis of the promoter activities of Arabidopsis ACC synthase genes AtACS4, AtACS5, and AtACS7 induced by hormones and stresses

Ethylene biosynthesis in higher plants is regulated developmentallyand environmentally. To investigate the regulation of ACC synthasegene expression, the promoters of Arabidopsis ACS genes, AtACS4,AtACS5, and AtACS7, were fused to a GUS reporter gene, and therecombinant transgenes were introduced into Arabidopsis to producethree groups of AtACS::GUS transgenic plants. Histochemic andfluorometric study of these transgenic plants revealed thatpromoters of AtACS4, AtACS, and AtACS7 are all active in dark-germinatedseedlings. AtACS5 has the highest promoter activity in leavesof 2-week-old light-grown seedlings among the three AtACS genesstudied. In the mature leaves, AtACS4 and AtACS7 genes are expressedin both veins and areoles, whereas AtACS5 is expressed at ahigher level in the areoles and epidermal cells surroundingtrichomes. The promoter activities of all these AtACS genesare found in the reproductive organs. AtACS5 and AtACS7 arehighly expressed in petals, sepals, carpels, stamens, caulineleaves, inflorescence stems, and siliques, while AtACS4 expressionis undetectable in the petals of open flowers. All three AtACSgenes are expressed in root tissue. In the 2-week-old light-grownArabidopsis, the AtACS4 promoter is responsive to the planthormones IAA, ethylene, and ABA, and to darkness and wounding;the AtACS5 promoter to IAA, ABA, salt, high temperature, andwounding; and the AtACS7 promoter to GA₃, ethylene, and ABA,and to darkness and salt. Low-temperature treatment abolishesthe darkness-induced AtACS7 gene expression, but not that ofAtACS4. Each AtACS gene has a unique expression profile duringgrowth and development. It appears that at any developmentalstage or any growth period of Arabidopsis, there is always amember of AtACS multigene family that is actively expressed. Key words: ACC synthase, Arabidopsis, ethylene, gene expression, GUS histochemical staining, reporter, stress treatments     

The Identification of the Seeds of the British Papaveraceae

The morphology of seeds of British wild, introduced, and commonlycultivated members of the Papaveraceae has been examined, anda key to the identification of the seeds is presented. Quantitative data on size and weight as well as informationabout shape, colour and surface features of the seeds are givenfor Papaver rhoeas L., P. dubium L., P. lecoqii lamotte, P.hybridum L., P. argemone L., P. somniferum L., P. lateritiumC. Koch, P. atlanticum (Ball) Coss., P. orientale L., P. nudicauleL., Meconopsis cambrica (L.) Vig., M. betonicifolia French,Roemeria hybrida (L.) DC., Glaucium flavum Crantz., G. corniculatum(L.) Rudolph, Chelidonium majus L., Eschscholzia californicaCham., E. erecta cv. compacta and E. erecta cv. miniature. Arepresentative sample of each seed is illustrated.     

Intergeneric and Interspecific Relationships in Araceae tribe Caladieae and Development of Molecular Markers using Amplified Fragment Length Polymorphism (AFLP)

Since amplified fragment length polymorphism (AFLP) analysishas proved useful in distinguishing cultivars of Caladium, itwas used to assess the status of species of Caladium vs. Xanthosoma,both in tribe the Caladieae, and to reassess the position ofHapaline in the same tribe. AFLP analysis using three primercombinations was carried out on four species of Caladium(C.bicolor, C. humboldtii, C. lindenii and C. schomburgkii). Resultsshowed that AFLP can distinguish between the different speciesby their unique and different banding patterns. AFLP analysisconfirmed that C. humboldtii is a species distinct from C. bicolorand that C. lindenii is a true Caladium species and does notbelong to Xanthosoma. UPGMA cluster analysis showed that C.bicolor and C. schomburgkii are most similar and that C. humboldtiiis closer to the C. bicolor / C. schomburgkii cluster comparedwith C. lindenii. Genetic relationships between Caladium, Xanthosoma,Hapaline, Alocasia and Protarum were also examined by AFLP analysisusing eight primer combinations. Several useful molecular markerswere specific either to Caladium orXanthosoma , so that AFLPcan be used to distinguish species of these two genera. Geneticanalysis of the genera examined confirms that the Caladieaeand Colocasieae tribes are distinct and that Hapaline fallswithin the tribe Caladieae and that Protarum is most distantfrom all the genera examined. Copyright 2000 Annals of BotanyCompany Araceae, Caladium, Xanthosoma, Hapaline, Alocasia, Protarum, AFLP DNA fingerprinting, diversity, AFLP markers     

Cytochrome components of green alga, Bryopsis maxima

Five soluble cytochromes were isolated and were partially purifiedfrom Bryopsis maxima: Cytochrome b-562 is slightly autoxidizable and has a midpointredox potential of +175 mV at pH 7.0. Its molecular weight isclose to 30,000 as estimated by dextran gel filtration. Cytochrome b-555 is autoxidizable and can be reduced by dithionitebut not by ascorbate. Cytochrome c-549 is a basic protein. It is slightly autoxidizableand reducible with either ascorbate or dithionite. Cytochrome c-549_(LP) is autoxidizable and reducible with dithionitebut not with ascorbate. The reduced cytochrome combines withcarbon monoxide. Cytochrome c-553 is the f-type one, which was reported by Sugimuraet al. (1968). ¹ This paper is dedicated to the memory of the late Prof. AtusiTakamiya at Toho University. (Received September 10, 1976; )     

Effects of rotifers and ciliates on the growth and survival of Daphnia

Daphnia can suppress ciliates and rotifers through predationand interference competition, but it is not known whether thisproduces any direct benefit to Daphnia. We conducted survivorshipand cohort lifetable experiments to determine whether Daphniacan utilize ciliates and rotifers as food. Three species ofoligotrich ciliates (Halteria grandinella, Strobilidium gyransand Strobilidiumvelox) and one rotifer (Keratella cochlearis)were used. Lifetable experiments were conducted with a basallevel of algae (Cryptomonas sp.), plus either ciliates or rotifers,while survivorship experiments had only the rotifers or ciliates.Densities of 30 H.grandinella ml^–1, 50 S.gyrans ml^–1and 15 S.velox ml^–1 enhanced Daphnia pulex's populationgrowth rate 35–50% over controls with only algae. TenS.gyrans ml^–1 did not produce a significant change inDaphnia's growth rate. Densities of 100 and 300 K.cochlearis^–1 increased Daphnia population growth rates by II and10%, respectively. Both 10 and 50 S.gyrans ml^–1 enhancedDaphnia's survivorship compared to starved controls, but neither100 nor 300 K.cochlearis l^–1 enhanced its survivorship.The amount of enhancement of Daphnia growth rates by rotifersand ciliates is roughly proportional to the death rates imposedby Daphnia. The death rate imposed by Daphnia on rotifers isa function of both algal density and Daphnia size. Per unitbiomass, neither ciliates nor Keratella appear to be as nutritiousfor Daphnia as is Cryptomonas.     

FLC or not FLC: the other side of vernalization

Vernalization is the promotion of the competence for floweringby long periods of low temperatures such as those typicallyexperienced during winters. In Arabidopsis, the vernalizationresponse is, to a large extent, mediated by the repression ofthe floral repressor FLC, and the stable epigenetic silencingof FLC after cold treatments is essential for vernalization.In addition to FLC, other vernalization targets exist in Arabidopsis.In grasses, vernalization seems to be entirely independent ofFLC. Here, the current understanding of FLC-independent branchesof the vernalization pathway in Arabidopsis and vernalizationwithout FLC in grasses is discussed. This review focuses onthe role of AGL19, AGL24, and the MAF genes in Arabidopsis.Interestingly, vernalization acts through related molecularmachineries on distinct targets. In particular, protein complexessimilar to Drosophila Polycomb Repressive Complex 2 play a prominentrole in establishing an epigenetic cellular memory for cold-regulatedexpression states of AGL19 and FLC. Finally, the similar networktopology of the apparently independently evolved vernalizationpathways of grasses and Arabidopsis is discussed. Key words: AGL19, Arabidopsis, chromatin, epigenetics, FLC, flowering time, polycomb, PRC2, vernalization Received 19 December 2007; Revised 11 February 2008 Accepted 15 February 2008     

Biomechanical Attributes of the Leaves of Pine Species

The flexural stiffness EI, elastic modulus E, second momentof area I, length L, and weight Wt of foliage leaves from 26species of pine were measured to determine the manner in whichEI is scaled to leaf size (L or Wt, or both) and to determineif the biomechanical attributes of foliage leaves could be juxtaposedwith the systematic affiliations of species within Pinus Biomechamcaland morphometric data were explored based on a model from engineeringtheory that predicts the relationships among EI, Wt and L providedthat the maximum tip-deflection _max of an untapered cantileveredbeam sustaining its own weight is maintained as the beam eitherincreases in length or weight, or both, I e _max = Wt L²/8EIThe data show that EI disproportionately increased as eitherWt or L, or both increased The allometry of leaves did not conformto that predicted by the model Rather, EI was proportional tothe product of Wt and L raised to an exponent slightly greaterthan one Thus, Omax was predicted not to be maintained as eitherWt or L, or both, increased, as verified by observations Therelationship between El and Wt(L) differed for species typicallyproducing two leaves per fascicle and those bearing more thantwo leaves per fascicle Also, El is geometrically constrainedby the number of leaves produced per fascicle, principally interms of the effects of the number of leaves per fascicle onI Pinus, pine, leaves, biomechanics, Young's modulus     

A Mechanistic Analysis of Self-thinning in Terms of the Carbon Balance of Trees

The self-thinning behavior of a monoculture forest is examinedfrom a mechanistic viewpoint, in terms of the carbon balanceof trees at the stand level. Two approaches are described: thefirst is based on simple assumptions concerning the balancebetween growth, photosynthesis and respiration; the second usesthe process-based I.T.E. EDINBURGH FOREST model, extended toinclude tree birth and death, to examined the assumptions ofthe first approach at a more mechanistic level and to interpretthe observed variation in the responses to shading and soilfertility in terms of a single model. The first approach leads to a power law relation m n ^-1/y betweenmean biomass per tree (m) and the number of trees per unit groundarea (n), where y is the exponent characterising the rate atwhich respiration (r) scales with biomass (i.e. r m^y). Forvalues of y less than 1, m and n are predicted to increase anddecrease, respectively, as powers of time (t) such that thebiomass per unit ground area (M) increases linearly with t forany value of y. When y equals 1, m and n vary exponentiallywith t and M remains constant. When r is assumed to be proportional to stem cambium surfacearea, the value of y is shown to lie in the range 0·5to 1 depending on the rate of stem taper. This leads to slopeson a log m vs. log n self-thinning plot in range -1 to -2 andtypically around -1·5 for rates of taper based on mechanicalrequirements. For the second approach, the I.T.E. EDINBURGH FOREST model,a previously published mechanistic model of plantation growthat the stand level (Thornley, 1991), is extended to naturalstands by introducing average stem birth and death rates thatare functions of the carbon and nitrogen substrate status oftrees. Growth of even-aged and mixed-age forest over about 500years is simulated under a variety of environmental and physiologicalconditions. In general, the forest model predicts a curved log m vs. logn thinning line, but has a reasonably well-defined linear sectionunder most conditions. The slope of the linear portion flattensas the rate at which cambium surface area scales with structuralbiomass increases, in qualitative agreement with the analyticalprediction of the first approach. Quantitative differences betweenthe two approaches are interpreted in terms of the process representedin the forest model. In general, the height of the thinningline increases with irradiance, but is relatively insensitiveto soil nitrogen, with no change in slope in either case. However,at very low irradiance or soil nitrogen levels, the slope flattenscontinuously and the entire thinning line becomes markedly non-linear.Even-aged stands and mixed-age stands have different thinningslopes.Copyright 1993, 1999 Academic Press Self-thinning, carbon balance, mechanistic model, forest growth, respiration     

Differential Expression of Genes Involved in the Biosynthesis and Perception of Ethylene during Ripening of Passion Fruit (Passiflora edulis Sims)

An increase in the enzyme activity of 1-aminocyclopropane-1-carboxylicacid (ACC) synthase and ACC oxidase induces the evolution ofethylene during the ripening of passion fruit. A much higherlevel of ethylene is produced in arils than in seeds or peelsduring ripening. The pattern of expression of two ACC synthasegenes (PE-ACS1 and PE-ACS2), one ACC oxidase gene (PE-ACO1),and two ethylene receptor genes (PE-ETR1 and PE-ERS1) revealedthat the expression of these genes is differentially regulated.Expression of PE-ACS1 and PE-ACO1 was enhanced during ripeningand after ethylene treatment. However, prominent expressionof PE-ACS1 was delayed compared to that of PE-ACO1. Much largerquantities of PE-ACS1 mRNA and PE-ACO1 mRNA were seen in arilsthan in seeds; this corresponds well with an increase in theamount of ethylene produced by the plant tissue itself. Thelevel of PE-ACS2 mRNA was detectable in arils of the preclimactericfruit, although it decreased during ripening. These resultssuggest that expression of PE-ACS1 and PE-ACO1 is required toincrease the activity of ethylene biosynthetic enzymes duringripening. The level of expression of PE-ETR1 and PE-ERS1 didnot significantly change over the course of ripening; however,the mRNA levels of PE-ETR1 and PE-ERS1 were much higher in arilsthan in seeds. ⁴Present address: Center forMolecular Genetics Research, Shizuoka University, Shizuoka, 422-8529 Japan.     

Genetic Diversity of the Wild Banana Musa acuminata Colla in Malaysia as Evidenced by AFLP

Musa acuminata Colla (Musaceae), the wild progenitor of thecultivated banana, is highly variable in Malaysia and presentsseveral unresolved nomenclatural problems. AFLP was employedto distinguish among three subspecies of Musa acuminata(subsp.truncata and subsp. malaccensis from peninsular Malaysia andsubsp. microcarpa from Borneo) and to examine whether subsp.truncata is a distinct taxon. Eight primer combinations revealedmolecular markers specific for each of the three taxa. UPGMAcluster analysis showed the three taxa were distinct. Subspeciesmalaccensis which is endemic in peninsular Malaysia and subsp.microcarpa which is endemic in Borneo were found to be moresimilar to each other in their DNA patterns than they are tosubsp. truncata, which is endemic to peninsular Malaysia. Sincesubsp. truncata is genetically separate from subsp. malaccensisand subsp.microcarpa , it cannot be regarded as synonymous witheither of these subspecies. This paper sheds light on the nomenclatureof the three subspecies of Musa acuminata. Copyright 2001 Annalsof Botany Company Musa acuminata Colla, truncata, malaccensis, microcarpa, Musaceae, wild banana, genetic diversity, AFLP, DNA fingerprinting     

An Analysis of Growth of Oil Palms under Nursery Conditions: II. The Effect of Spacing and Season on Growth

Three experiments on the growth of watered nursery oil palmsare described, the results of which provide estimates of seasonalvariation in net assimilation rate (E_A) and relative growth-rate(R_w) in the tropics (6° 33' N.). The range of values obtained for E_A and R_w is similar to thatfound with seedlings and during early growth in the nursery(E_A = o.I8–o.32 g/dm²/week, R_w= o.84–I.70 per cent/day)and there is very little effect of season on E_A; such variationas exists appears to be related to solar radiation. A spacing experiment indicated that E_A is independent of leafarea index (L) when L is below about 2.2, but that above thislevel E_A decreases with increasing L, falling to zero at L =5.4. The crop growth-rate (C) is maximal when L is between 2.5and 3, the maximum value observed was o.62 g/dm²/week (equivalentto 3.22 x10⁴ kg/ha/annum). These results are compared with other estimates of growth andassimilation rates of seedling, nursery and adult oil palms,and are discussed in relation to the efficiency of energy fixation,and apparent growth-rates.     

Predation impact of Cyclops vicinus on the rotifer community in Lake Constance in spring

The predation impact of Cyclops vicinus on rotifers was studiedunder near-natural conditions in small enclosures to evaluatewhether copepod predation is responsible for the decline ofrotifers in Lake Constance in spring. Cyclops vicinus fed selectivelyon Synchaeta spp.; Keratella and Polyarthra spp. were not selectedfor. Predation rates increased with prey density up to a maximumof 37 Synchueta day^–1 at a density of 1.6 x 10⁶ Synchaetam^–2, i.e. at -1200 Synchaeta l^–1. Calculation ofcropping rates suggests that Cyclops alone can control the abundanceof Synchaeta in spring, i.e. that mainly Cyclops is responsiblefor the decline of Synchaeta species in Lake Constance in May.     

Evaluation of nitrogen fixation in the diatom genus Rhizosolenia Ehr. in the absence of its cyanobacterial symbiont Richelia intracellularis Schmidt

Aggregates of two species of Rhizosolenia (R. castracanei andR. imbricata var. shrubsolei) have been reported to containendosymbiotic bacteria and to fix nitrogen. The general importanceof this process to the genus is not known, although of greatpotential significance. Clonal cultures of five species of Rhizosolenia(R. alata, R. bergonii, R. calcar-avis, R. imbricata var. shrubsoleiand R. setigera) were examined for nitrogen fixation using acetylenereduction and compared to cyanobacterial controls. Mecososmaggregates of R. imbricata var. shrubsolei were tested, as wellas chains of R. debyana hand-collected using SCUBA. The Rhizosoleniaspecies did not contain the endosymbiotic cyanobacterium Richeliaintracellularis and were not examined for the presence of endosymbioticbacteria. Nitrogen fixation was not found in the Rhizosoleniaspp.; in contrast, the diazotrophic cyanobacterial controlsOscillatoria erythraea and Anabaena sp. reduced acetylene atsignificant rates. The absence of nitrogen fixation in the Rhizosoleniaspp. suggests diazotrophy by endosymbiotic bacteria is not widespreadin the genus Rhizosolenia, nor is it necessary for survivalof these large diatom cells in nutrient-poor, near-shore waters.     

Some Observations on the Diversity of Stomata and Trichomes in Six Species of Dioscorea

Stomata and trichomes are described on the leaves of six speciesof Dioscorea. As many as six types were found in D. bulbiferaand D. oppositifolia, four types in D.hispida and D. wallichii,three types in D. belophylla, but only two types in D. alata.Although there is a diversity of stomata even on the same surface,the predominant type is anomocytic in all the species exceptD. bulbifera in which it is tricytic. Rarely a stoma is alsocyclocytic in D. bulbifera. An increase in the number of subsidiarycells in paracytic, tricytic, or diacytic stomata takes placeby the wall formation in them. Similarly a reduction in thenumber of subsidiary cells of a tetracytic stoma is the resultof lateral subsidiary cells assuming the form of epidermal cells.Abnormalities such as a stoma with one guard cell, degenerationof guard cells, and contiguous stomata are also met with. Theorganization of different types of stomata is studied in D.bulbifera and D. wallichii and shown to be perigenous. Capitateglandular hairs were seen on the leaves of D. belophylla, D.bulbifera, D. hispida, and D. wallichii but non-glandular, uniseriate,3-celled trichomes were observed only in D. hispida.     

Molecular Cytogenetics of the Genus Arabidopsis: In situ Localization of rDNA Sites, Chromosome Numbers and Diversity in Centromeric Heterochromatin

We have used in situ hybridization to determine the number ofsites of rDNA in species in the genus Arabidopsis. A. wallichii(2n = 16) has one major pair of sites and one minor pair ofsites, while A. pumila and A. griffithiana (both 2n = 32) havesix major and two minor rDNA sites. A. thaliana (2n = 10) isknown to have two pairs of rDNA sites. a highly repeated para-centromericsequence from A. thaliana, pAL1, is absent in the other threespecies. Hence the A.thaliana genome is not present (or thecentromeric DNA has evolved substantially) in the polyploidspecies A. pumila and A. griffithiana. Analysis of Arabidopsisspecies is a valuable complement to the large programmes forgenetic analysis of A. thaliana.Copyright 1993, 1999 AcademicPress Arabidopsis, centromeric DNA, maps (genetic), nuclear architecture, repetitive DNA, ribosomal DNA, rDNA, evolution, Brassicaceae, Crucifereae, in situ hybridization     

Shell characters and taxonomy of Latirus and related fasciolariid groups

The neogastropod family Fasciolariidae contains a complex ofgenera related to Latirus Montfort, 1810, many of which havetraits unusual for the family. In a taxonomic revision of someof these genera, based on shell characters, we restrict Latirusto a mainly Indo-West Pacific group of Pliocene to Recent species,which closely resemble the middle Miocene to Recent pantropicalgenus Hemipolygona Rovereto, 1899. Hemipolygona stenomphalus(Habe & Kosuge, 1966) is synonymized with H. recurvirostris(Schubert & Wagner, 1829). Lathyropsis Oostingh, 1939, basedon a small Pliocene species from Indonesia, is here tentativelysubsumed under Polygona Schumacher, 1817. The latter genus,ranging from the late Oligocene to Recent, occurs mainly inthe New World and eastern Atlantic, and contains at least twospecies groups centered on P. infundibulum Schumacher, 1817(type of genus) and P. angulatus (Röding, 1798). Taxa assignedby many authors to Latirulus Cossmann, 1889, are here reassignedto the new genus Turrilatirus (type species: Voluta turritaGmelin, 1791), from the Pliocene to Recent of the Indo-WestPacific. Latirulus is restricted to Eocene species. We assignvarious early Miocene to Recent species from the western Atlanticand eastern Pacific to the new genus Pustulatirus (type species:Latirus mediamericanus, Hertlein & Strong, 1951a). Taxaformerly assigned to Latirus but here removed from Fasciolariidaeinclude Latirus ewekoroensis Adegoke, 1977; the Eocene RusculaCasey, 1904; Lathyrus granifer and L. compactilis, both of Martin,1931; Latirus kirbyi Clark, 1938; Latirus tortilis var. nanafaliusHarris, 1899; and Latirus quercotillaensis Olsson, 1931. (Received 6 September 2005; accepted 29 May 2006)     

A Study of the Evolutionary Relationships of Fundulus Topminnows (Teleostei: Fundulidae)

A hypothesis of the evolutionary relationships of thirty-fourspecies of Fundulus and their closer relatives is presented.The study is restricted to morphological characters which couldbe determined to be primitive or derived using the methods ofphylogenetic systematics. Following Parenti, a family Fundulidaeis recognized. It is composed of four genera of North Americankillifishes. (Cyprinodontidae as usually constitutedis polyphyletic.)No convincing characters demonstrate that Fundulus is a naturalgroup (a monophyletic group). However, all species of Fundulusshare four derived characters with Lucania. The sister group(closest genealogical relative) of Fundulus plus Lucania isa group composed of the genera Adinia and Leptolucania. Fourmonophyletic groups of Fundulus can be recognized based on sharedderived characters: (1) subgenus Fundulus (seven species excludingthree species placed in Fontinus); (2) subgenus Fonlinus (sixspecies); (3) subgenus Xensima (five species); and (4) subgenusZygonectes (thirteen species). Three species, F. (Plancterus)zebrinus, F. lima, and F. parvipinnis are of uncertain affinitieswithin the Lucania-Fundulus clade