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At least 1,171 records · Page 65Linked to original sources
PubMed1990

Inbred testing of tomato (Lycopersicon esculentum L.) F1 varieties by ultrathin-layer isoelectric focusing of seed protein.

To test seed lots of tomato F1 hybrid varieties for the presence of undesirable inbred seeds by electrophoresis, a method has been developed on the basis of ultrathin-layer isoelectric focusing. The method is based on the genetic variation of the seed protein PRS-1 which could be visualized by isoelectric focusing of a 5 mM NaCl-soluble seed protein extract in a pH 6-9 gel followed by protein staining. Two genetic variants of the PRS-1 protein, PRS-1+ and PRS-1(1), were found among open-pollinated varieties, as well as among F1 hybrid varieties. The isoelectric points (pI) of the PRS-1 proteins are 7.1 and 6.1 for PRS-1+ and PRS-1(1), respectively. The PRS-1 protein is unique to seed tissue and is located primarily in the embryo. A genetic 1:2:1 segregation of the gene Prs-1 among several F2 populations shows monogenic inheritance. Analysis of commercial F1 hybrid varieties from several seed companies indicated that the Prs-1(1) allele, in contrast to the Prs-1+ allele, is primarily present in gene pools of "Money-maker type" tomatoes. The described method is generally applicable to all tomato F1 varieties that are heterozygous for the gene Prs-1. With the described method one person can routinely analyze more than 768 seeds per day.

Alleles↗
PubMed1995

Application of DNA fingerprinting to the taxonomy of European blackberry species.

Thousands of blackberry species (Rubus subgenus Rubus) have been described from Central and Northern Europe. These species are usually polyploid and pseudogamous. Since apomixis is only facultative, the species have retained the possibility to produce some offspring by sexual recombination. Hybridization of restriction-enzyme-digested DNA samples to the M13, (AC)/(TG) and 33.15 probes has yield valuable information on the occurrence and distribution of genetic variation in Rubus. Intraspecific variation proved to be very restricted, with identical DNA fingerprints sometimes being exhibited by Swedish, Danish and German populations of the same species. By comparison, interspecific variation was usually pronounced, suggesting that most species have been derived through genetic recombination. Speciation through interspecific hybridization was demonstrated in one case. Several critical taxa were investigated; some of these proved to have unique DNA fingerprints, whereas others appear to be identical with previously described species. Evaluation of raspberry cultivars, obtained through several generations of vegetative propagation or with various in vitro techniques, failed to detect any DNA fingerprint variation, suggesting that the fingerprints are somatically stable. Blackberry seedlings, obtained by pollinating various species as well as interspecific hybrids with pollen from yet other species, were successfully evaluated with DNA fingerprinting to determine the relative proportions of the apomictic and sexual seed set.

DNA Fingerprinting↗
PubMed1985

Liposome-mediated transformation of tobacco mesophyll protoplasts by an Escherichia coli plasmid.

An Escherichia coli plasmid, pLGV23neo, carrying a kanamycin resistance gene expressed in plant cells, was encapsulated into negatively charged liposomes prepared by the reverse phase evaporation technique. These liposomes were induced to fuse with tobacco mesophyll protoplasts by polyethyleneglycol treatment. Kanamycin-resistant clones were reproducibly isolated from transfected cultures at an average frequency of 4 X 10(-5). Plants regenerated from these resistant colonies were confirmed to be transformed according to three criteria. Protoplasts isolated from their leaves were resistant to 100 micrograms/ml kanamycin. The enzyme aminoglycoside 3'-phosphotransferase II encoded by the plasmid pLGV23neo was detected in leaf extracts. Approximately 3-5 copies of the gene encoding for kanamycin resistance were inserted in the genome of at least one of the studied transformants. The restriction pattern of inserted DNA was best explained by assuming a tandem integration of the pPLGV23neo sequences, implying an homologous recombination event between these sequences during transformation. Kanamycin resistance was transmitted as a single dominant nuclear marker to the progeny of resistant plants after selfing or cross-pollination with the wild-type.

Aminoglycosides↗
PubMed1985

Accumulation and assembly of soybean beta-conglycinin in seeds of transformed petunia plants.

A gene encoding the alpha'-subunit of beta-conglycinin, a seed storage protein of soybean (Glycine max), was transformed into petunia cells on a disarmed Ti-plasmid of Agrobacterium tumefaciens, and plants were regenerated. Transcripts of the introduced gene accumulated in immature embryos but not in leaves of the transformed plants. Soybean protein was first detected immunologically in proteins extracted from embryos at 10 days post pollination (d.p.p.), concurrent with the accumulation of subunits of the major petunia seed proteins. Between 10 and 16 d.p.p. the primary soybean protein detected had an apparent mol. wt. of 55 kd. The 76-kd alpha'-subunit and several smaller polypeptides accumulated between 16 and 24 d.p.p., when seeds had matured. Polypeptides <76 kd probably resulted from specific proteolytic cleavage of the alpha'-subunit. The alpha'-subunit and the smaller polypeptides assembled into multimeric proteins with sedimentation coefficients of 7-9S, similar to the sedimentation coefficients of beta-conglycinins isolated from soybean seeds. This transformation and expression system should be ideally suited for testing gene mutations to alter the amino acid composition of these seed storage proteins.

Journal Article↗
PubMed1976

Feeding adaptations in the hairs and tongues of nectar-feeding bats.

Scales on the hairs of pollinating bats spread out at an angle to the main hair shaft. In contrast, the hairs of most bats not associated with plants are relatively smooth. Both megachiropteran and microchiropteran flower-feeding bats show this divaricate scale structure which may aid in the collection of a heavy coating of pollen. Some of the pollen is transferred to subsequent flowers, but most is groomed from the fur and ingested as the only reliable nitrogen source for the bat. The tongues of nectar-feeding bats also show structural modifications which allow efficient uptake of the carbohydrate fraction of the diet. Structural specializations of the hiars and tongue are analogous to those seen in other nectar-feeding animals.

Adaptation, Biological↗
PubMed2005

Technical performance of some commercial glyphosate-resistant crops.

Glyphosate-resistant (GR) crops have been sold commercially in the USA since 1996. The use of glyphosate alone or with conventional pre- and post-emergence herbicides with different modes of action gives growers many options for affordable, safe, easy, effective wide-spectrum weed control. Despite the overwhelming popularity of this technology, technical issues have surfaced from time to time as US growers adopt these crops for use on their farms. The types of concern raised by growers vary from year to year depending on the crop and the environment, but include perceptions of increased sensitivity to diseases, increased fruit abortion, reduced pollination efficiency, increased sensitivity to environmental stress, and differences in yield and agronomic characteristics between transgenic and sister conventional varieties. Although several glyphosate-resistant crops are commercially available, maize, soybean and cotton constitute the largest cultivated acreage and have likewise been associated with the highest number of technical concerns. Because glyphosate is rapidly translocated to and accumulates in metabolic sink tissues, reproductive tissues and roots are particularly vulnerable. Increased sensitivity to glyphosate in reproductive tissues has been documented in both glyphosate-resistant cotton and maize, and results in reduced pollen production and viability, or increased fruit abortion. Glyphosate treatments have the potential to affect relationships between the GR crop, plant pathogens, plant pests and symbiotic micro-organisms, although management practices can also have a large impact. Despite these potential technical concerns, this technology remains popular, and is a highly useful tool for weed control in modern crop production.

Crops, Agricultural↗
PubMed2002

Effect of surface material on electrostatic charging of houseflies (Musca domestica L).

Houseflies (Musca domestica L) accumulated electrostatic charges when walking over clean, uncharged dielectric surfaces. The charges elicited on a walking housefly by a range of materials were quantified, allowing a triboelectric series to be determined relative to M domestica. This ranged from surfaces that charged individuals positively, e.g. Correx (corrugated polypropylene) [.1 (+/- 4.2)pC], to those that applied a negative charge, e.g. clear cast acrylic [-14.9 (+/- 2.9)pC]. Maximum positive and negative charges accumulated by individual M domestica were +73 and -27 pC. Replicate measurements on the same fly and surface showed little variation. Variation between individuals was not related to sex and was not consistent between surfaces. Different materials charged M domestica significantly differently and individual flies had significantly different charging properties. Variation in temperature between 21.3 degrees C and 24.7 degrees C and humidity between 24% and 41% RH significantly affected charge accumulated by M domestica on some surfaces, although further experimentation is needed to confirm this. The implications of this work are discussed in relation to insect trap design and pollination biology.

Acetals↗
PubMed1995

Purification and characterization of S-linalool synthase, an enzyme involved in the production of floral scent in Clarkia breweri.

S-Linalool is one of the volatiles emitted by Clarkia breweri Grey [Green] flowers to attract its moth pollinator. S-Linalool synthase, the enzyme that stereoselectively converts the ubiquitous C10 intermediate GPP to S-linalool, is abundant in stigmata of freshly opened flowers, and it was purified to > 95% homogeneity by anion-exchange and hydroxyapatite chromatography. S-Linalool synthase is operationally soluble as are other monoterpene synthases, has a Km of 0.9 microM for geranyl pyrophosphate, exhibits a strict requirement for a divalent metal cofactor with a preference for Mn2+ (Km = 45 microM), and shows an optimal pH of 7.4. The enzyme is active as a monomer of 76 +/- 3 kDa as determined by gel permeation chromatography and polyacrylamide gel electrophoresis. Neither S- nor R-linalyl pyrophosphates are substrates for the C. breweri S-linalool synthase, although this tertiary allylic pyrophosphate ester is a bound intermediate in the biosynthesis of cyclic monoterpenes from geranyl pyrophosphate in many plant species, where it also serves as an alternate substrate.

Acyclic Monoterpenes↗
PubMed1999

Cloning, expression, and characterization of epi-cedrol synthase, a sesquiterpene cyclase from Artemisia annua L.

Sesquiterpene cyclases (synthases) catalyze the conversion of the isoprenoid intermediate farnesyl diphosphate to various sesquiterpene structural types. In plants, many sesquiterpenes are produced as defensive chemicals (phytoalexins) or mediators of chemical communication (i.e., pollinator attractants). A number of sesquiterpene synthases are present in Artemisia annua L. (annual wormwood). We have isolated a cDNA clone encoding one of these, epi-cedrol synthase. This clone contains a 1641-bp open reading frame coding for 547 amino acids (63.5 kDa), a 38-bp 5'-untranslated end, and a 272-bp 3'-untranslated sequence. The deduced amino acid sequence was 32 to 43% identical with the sequences of other known sesquiterpene cyclases from angiosperms. When expressed in Escherichia coli, the recombinant enzyme catalyzed the formation of both olefinic (3%) and oxygenated (97%) sesquiterpenes from farnesyl diphosphate. GC-MS analysis identified the olefins as alpha-cedrene (57% of the olefins), beta-cedrene (13%), (E)-beta-farnesene (5%), alpha-acoradiene (1%), (E)-alpha-bisabolene (8%), and three unknown olefins (16%) and the oxygenated sesquiterpenes (97% of total sesquiterpene generated, exclusive of farnesol and nerolidol) as cedrol (4%) and epi-cedrol (96%). epi-Cedrol synthase was not active with geranylgeranyl diphosphate as substrate, whereas geranyl diphosphate was converted to monoterpenes by the recombinant enzyme at a rate of about 15% of that observed with farnesyl diphosphate as substrate. The monoterpene olefin products are limonene (45%), terpinolene (42%), gamma-terpinene (8%), myrcene (5%), and alpha-terpinene (2%); a small amount of the monoterpene alcohol terpinen-4-ol is also produced. The pH optimum for the recombinant enzyme is 8.5-9.0 (with farnesyl diphosphate as substrate) and the K(m) values for farnesyl diphosphate are 0.4 and 1.3 microM at pH 7. 0 and 9.0, respectively. The K(m) for Mg(2+) is 80 microM at pH 7.0 and 9.0.

Amino Acid Sequence↗
PubMed2000

Intersexual sibling interactions and male benevolence in a fig wasp.

We studied interactions between males and females of the Australian pollinating fig wasp, Pleistodontes imperialis (Chalcidoidea, Agaonidae), in Ficus platypoda (Moraceae). As for many other fig wasps, all mating occurs within the confines of a syconium before females depart. We show that initially there is scramble competition between males for access to virgin females. During this time males excavated a small hole into a female's gall to mate through. These holes were just large enough for insemination, but not large enough for females to exit their galls. Males ignored mated females, and as virgin females became scarce males switched strategies and began to enlarge insemination holes until they were large enough for females to escape, showing that males enhance female fitness by means other than just mating. Syconia with experimentally reduced numbers of males had fewer liberated females, suggesting that female fitness is strongly affected by the number of males present. Females may be unable to escape their galls unassisted because of morphological adaptations to syconium founding. We argue that sex allocation should be affected not only by competition among males but also by intersexual interactions between siblings. This could potentially offset the strong female bias predicted by local mate competition. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1995

The appearance of male gamete-specific histones gH2B and gH3 during pollen development in Lilium longiflorum.

The male gametic (generative) nucleus within the nearly mature pollen of Lilium longiflorum contains specific variants of histone H2B and H3, which have been designated gH2B and gH3, respectively. Using specific antibodies raised against gH2B and gH3, we examined in detail the temporal and spatial aspects of the appearance of these histone variants during male gametogenesis. Neither gH2B nor gH3 was detected in microsporocytes during meiotic division or in microspores before microspore mitosis. However, both gH2B and gH3 were abundantly present in mid bicellular pollen and these histones continued to be detectable in germinated pollen tubes after pollination. Furthermore, immunocytochemistry revealed that these proteins were present not only in generative nuclei during the maturation process, but also in the two sperm nuclei formed by division of the generative nucleus. By contrast, these proteins were not found in the vegetative nuclei. It appears, therefore, that both gH2B and gH3 are specific to male gametic (generative and sperm) nuclei in L. longiflorum. The results also suggest that these male gamete-specific histones might be newly synthesized in the progenitor of sperm cells for the differentiation of male gametes, as occurs in spermatogenesis in animals.

Cell Differentiation↗
PubMed1996

Isolated maize zygotes mimic in vivo embryonic development and express microinjected genes when cultured in vitro.

We established conditions for the regeneration of natural maize zygotes isolated from pollinated plants with the goal of investigating the molecular control of early embryogenesis in higher plants. Viable zygotes were excised from embryo sacs by minimal enzymatic digestion and microdissection. Viable zygotes transferred to coculture with androgenic microspores from barley developed into embryo-like structures in 61% of the cases. No development was observed when zygotes were cultured in the presence of maize anthers undergoing androgenetic embryogenesis. Zygote-derived embryo-like structures regenerated into fertile plants through secondary embryogenesis when transferred to solid medium. The first zygotic division was asymmetrical and bipolar structures similar to pretransitional embryos observed in planta were later produced as observed using light and electron microscopy. Conditions for efficient microinjection of DNA into zygotes were established. Calcofluor and PATAG staining of zygotes showed that cell wall regeneration occurred as early as 20 min after enzymatic isolation and that after 2 hr, each zygote was bordered with cell wall material. Through quantitative microphotometry, DNA synthesis during the first cell cycle of the zygote was shown to occur between isolation and 12 hr of culture. Microinjection of two types of reporter genes (GUS gene and anthocyanin regulatory genes) demonstrates transient expression in plant zygotes. On average, 3.5% of microinjected zygotes showed transgenic expression. Reporter gene expression was observed in zygotes at different time points of their first cell cycle.

Cell Cycle↗
PubMed2001

The 1.55 A resolution structure of Nicotiana alata S(F11)-RNase associated with gametophytic self-incompatibility.

The crystal structure of Nicotiana alata (ornamental tobacco) S(F11)-RNase, an S-allelic glycoprotein associated with gametophytic self-incompatibility, was determined by X-ray diffraction at 1.55 A resolution. The protein has a tertiary structure typical of members of the RNase T(2) family as it consists of a variant of the (alpha+beta) fold and has eight helices and seven strands. A heptasaccharide moiety is also present, and amino acid residues that serve as the catalytic acid and base can be assigned to His32 and His91, respectively. Two "hypervariable" regions, known as HVa and HVb, are the proposed sites of S-allele discrimination during the self-incompatibility reaction, and in the S(F11)-RNase these are well separated from the active site. HVa and HVb are composed of a long, positively charged loop followed by a part of an alpha-helix and short, negatively charged alpha-helix, respectively. The S(F11)-RNase structure shows both regions are readily accessible to the solvent and hence could participate in the process of self/non-self discrimination between the S-RNase and an unknown pollen S-gene product(s) upon pollination.

Amino Acid Sequence↗
PubMed1999

Phylogeny and evolution of Orchis and allied genera based on ITS DNA variation: morphological gaps and molecular continuity.

Phylogenetic relationships among members of genus Orchis and allied genera Aceras, Anacamptis, Barlia, Dactylorhiza, Gymnadenia, Himantoglossum, Neotinea, Ophrys, Platanthera, and Serapias were inferred from nucleotide sequence variation in the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA. Sequences were subjected to various alignments by changing the gap opening and extension parameters. After a preliminary parsimony analysis, the alignment with the lowest homoplasy indicators was chosen as optimal. The phylogenetic analysis, carried out on the optimal alignment by using Gennaria as an outgroup and a total of 31 taxa, showed that all the genera considered in this study are nested in Orchis despite their distinct morphological features. Genus Orchis is divided into two major clades, each of which includes one or more of the other genera in this study. The resulting phylogenetic hypothesis does not match previous conclusions based on vegetative and floral morphology of the taxa involved but is congruent with isoenzyme, karyological, and chloroplast DNA restriction data. Our results indicate that floral morphology is highly flexible and current generic and infrageneric limits are artificial. Even if some floral characters closely correspond to the molecular data, most are highly homoplastic and thus unsuitable for phylogenetic reconstruction. Various traits pertaining to floral morphology may be interpreted as a result of ecological convergence related to pollinator-mediated selection; such characters can undergo drastic modifications without correspondingly dramatic genetic changes.

Base Sequence↗
PubMed2001

A molecular phylogeny of Costaceae (Zingiberales).

The phylogenetic relationships of Costaceae, a tropical monocotyledonous family sister to the gingers (Zingiberaceae), were investigated with a combination of two chloroplast loci (the trnL-F locus, including the trnL intron, the 3'trnL exon, and the trnL-F intergenic spacer, and the trnK locus, including the trnK intron and the matK coding region) and one nuclear locus (ITS1-5.8s-ITS2). The resulting parsimony analysis of selected taxa that demonstrate the range of floral morphological variation in the family shows that the Cadalvena-type [corrected] floral morphology is ancestral to the group and that both Tapeinochilos species and a Monocostus + Dimerocostus clade represent recent divergences. The genus Costus is broadly paraphyletic but Costus subgenus Eucostus K. Schum. represents a large monophyletic radiation that is poorly resolved. Within this clade, secondary analyses suggest that pollination syndrome, traditionally used for taxonomic and classification purposes within the genus Costus, is a relatively plastic trait of limited phylogenetic utility. This represents the first detailed investigation into intrageneric and interspecific evolutionary relationships within the family Costaceae and presents some novel evolutionary trends with respect to floral morphology and biogeography.

Chloroplasts↗
PubMed1996

The stability and persistence of mutualisms embedded in community interactions.

In this paper we argue that two-species models of mutualism may be oversimplifications of the real world that lead to erroneous predictions. We present a four-species model of a pollination mutualism embedded in other types of community interactions. Conclusions derived from two-species models about the destabilizing effect of mutualisms are misleading when applied to the present scenario; although the mutualisms are locally destabilizing, the effect is more than canceled by an increased chance of feasibility. The crucial difference is the interaction of the mutualists with other species in a larger web. Furthermore, community persistence (without unrealistic population explosion), arguably a superior ecological criterion, is greatly enhanced by the presence of mutualisms. Therefore, we predict that mutualisms should be common in the real world, a prediction matching empirial findings and in contrast to the predictions from local stability analysis of basic two-species models. This method of stabilizing a mutualism appears superior in some ways to the often-used method of introducing density dependence in the strength of the mutualism, because it permits obligate mutualisms to exist even at low densities, again matching empirical findings. Lastly, this study is an example of how complex model assemblages can behave qualitatively differently from analogous simpler ones.

Animals↗
PubMed1996

Resistance to tomato yellow leaf curl geminivirus in Nicotiana benthamiana plants transformed with a truncated viral C1 gene.

The C1 gene of tomato yellow leaf curl geminivirus (TYLCV) encodes a multifunctional protein (Rep) involved in replication. A truncated form of this gene, capable of expressing the N-terminal 210 amino acids (aa) of the Rep protein, was cloned under the control of the CaMV 35S promoter and introduced into Nicotiana benthamiana using Agrobacterium tumefaciens. The same sequence was also cloned in antisense orientation. When self-pollinated progeny of 19 primary transformants were tested for resistance to TYLCV by agroinoculation, some plants proved to be resistant, particularly in the sense lines. Two such lines were further studied. The presence of the transgene was verified and its expression was followed at intervals. All plants that were resistant to TYLCV at 4 weeks postinoculation (wpi) contained detectable amounts of transgenic mRNA and protein at the time of infection. Resistance was overcome in a few plants at 9 wpi, and in most at 15 wpi. Infection of leaf discs derived from transgenic plants showed that expression of the transgene correlated with a substantial reduction of viral DNA replication. Cotransfections of tobacco protoplasts demonstrated that inhibition of viral DNA replication requires expression of the truncated Rep protein and suggested that the small ORF C4, also present in our construct, plays no role in the resistance observed. The results obtained using both transient and stable gene expression systems show that the expression of the N-terminal 210 aa of the TYLCV Rep protein efficiently interferes with virus infection.

Agrobacterium tumefaciens↗
PubMed2001

Genetic modification of plant secondary metabolite pathways using transcriptional regulators.

Plant secondary metabolism is the source of many natural products with diverse applications, including pharmaceuticals, food colors, dyes and fragrances. Functions in plants include attraction of pollinating insects and protection against pests and pathogens. An important regulatory step in secondary metabolism is transcription of the biosynthetic genes. The aim of this chapter is to discuss results and opportunities concerning modification of secondary metabolism using transcriptional regulators. The transcriptional regulation of two well-studied secondary pathways, the phenylpropanoid pathway and its flavonoid branch, and the terpenoid indole alkaloid biosynthetic pathway, are reviewed. Some examples of successful engineering of these pathways via transcriptional regulators are discussed.

Cyclopentanes↗