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PubMed2001

Inheritance of apospory in bahiagrass, Paspalum notatum.

Previous studies on the inheritance of aposporous apomixis in bahiagrass showed a wide range of segregation ratios in crosses involving sexual and aposporous apomictic plants. The F1 progenies were classified through a visual progeny test carried out on few F2 plants. The number of sexual F1s highly exceeded the apomictics leading to the conclusion that apomixis was controlled by a few recessive genes. The present study examines the inheritance of apospory in bahiagrass. A sexual plant was self-pollinated and crossed with an aposporous apomictic plant as pollen donor. Backcross and F2 progenies were obtained in several combinations. All self-pollinated sexual plants or sexual x sexual crosses produced progenies free of apospory. All crosses involving a sexual and an apomictic plant produced approximately three times more apospory-free plants than plants with apospory. Bahiagrass is of autotetraploid origin and hence is expected to display tetrasomic inheritance. The most widely accepted genetic model for inheritance of apospory in tropical grasses is a single dominant gene with tetrasomic inheritance. In the present experiments none of the apospory-free F1s segregated for the apospory trait indicating that it is most likely a dominant character. However, the observed results fit better a modified model: tetrasomic inheritance of a single dominant gene with pleiotropic effect and incomplete penetrance. The excess of apospory-free plants in the F1 progeny could be ascribed to some distortion in the segregation pattern due to a pleiotropic lethal effect of the dominant A allele with incomplete penetrance. Alternatively, partial lethality of factors linked to aposporous gene may account for segregation distortion against apospory.

Alleles↗
PubMed2001

Gene families from the Arabidopsis thaliana pollen coat proteome.

The pollen extracellular matrix contains proteins mediating species specificity and components needed for efficient pollination. We identified all proteins >10 kilodaltons in the Arabidopsis pollen coating and showed that most of the corresponding genes reside in two genomic clusters. One cluster encodes six lipases, whereas the other contains six lipid-binding oleosin genes, including GRP17, a gene that promotes efficient pollination. Individual oleosins exhibit extensive divergence between ecotypes, but the entire cluster remains intact. Analysis of the syntenic region in Brassica oleracea revealed even greater divergence, but a similar clustering of the genes. Such allelic flexibility may promote speciation in plants.

Alleles↗
PubMed2002

Rapid changes in flowering time in British plants.

The average first flowering date of 385 British plant species has advanced by 4.5 days during the past decade compared with the previous four decades: 16% of species flowered significantly earlier in the 1990s than previously, with an average advancement of 15 days in a decade. Ten species (3%) flowered significantly later in the 1990s than previously. These data reveal the strongest biological signal yet of climatic change. Flowering is especially sensitive to the temperature in the previous month, and spring-flowering species are most responsive. However, large interspecific differences in this response will affect both the structure of plant communities and gene flow between species as climate warms. Annuals are more likely to flower early than congeneric perennials, and insect-pollinated species more than wind-pollinated ones.

Climate↗
PubMed2004

RETRACTED: Darwinian selection on a selfing locus.

The shift to self-pollination is one of the most prevalent evolutionary transitions in flowering plants. In the selfing plant Arabidopsis thaliana, pseudogenes at the SCR and SRK self-incompatibility loci are believed to underlie the evolution of self-fertilization. Positive directional selection has driven the evolutionary fixation of pseudogene alleles of SCR, leading to substantially reduced nucleotide variation. Coalescent simulations indicate that this adaptive event may have occurred very recently and is possibly associated with the post-Pleistocene expansion of A. thaliana from glacial refugia. This suggests that ancillary morphological innovations associated with self-pollination can evolve rapidly after the inactivation of the self-incompatibility response.

Alleles↗
PubMed2006

Microarthropods mediate sperm transfer in mosses.

Among flowering plants, animals commonly act as pollinators. We showed that fertile moss shoots attract springtails and mites, which in turn carry moss sperm, thereby enhancing the fertilization process. Previously, fertilization of mosses was thought to depend on the capacity of individual sperm to swim through a continuous water layer. The role of microarthropods in moss fertilization resembles the role of animals as pollinators of flowering plants but may be evolutionarily much older because of the antiquity of the organism groups involved.

Animals↗
PubMed2006

A fossil bee from Early Cretaceous Burmese amber.

The bee fossil record is fragmentary, making it difficult to accurately estimate the antiquity of bee-mediated pollination. Here, we describe a bee fossil [Melittosphex burmensis (new species), Melittosphecidae (new family)] from Early Cretaceous Burmese amber (approximately 100 million years before the present). The fossil provides insights into the morphology of the earliest bees and provides a new minimum date for the antiquity of bees and bee-mediated pollination.

Amber↗
PubMed2002

Genetic diversity of Carica papaya as revealed by AFLP markers.

Genetic relationships among Carica papaya cultivars, breeding lines, unimproved germplasm, and related species were established using amplified fragment length polymorphism (AFLP) markers. Seventy-one papaya accessions and related species were analyzed with nine EcoRI-MseI primer combinations. A total of 186 informative AFLP markers was generated and analyzed. Cluster analysis suggested limited genetic variation in papaya, with an average genetic similarity among 63 papaya accessions of 0.880. Genetic diversity among cultivars derived from the same or similar gene pools was smaller, such as Hawaiian Solo hermaphrodite cultivars and Australian dioecious cultivars with genetic similarity at 0.921 and 0.912, respectively. The results indicated that self-pollinated hermaphrodite cultivars were as variable as open-pollinated dioecious cultivars. Genetic diversity between C. papaya and six other Carica species was also evaluated. Carica papaya shared the least genetic similarity with these species, with an average genetic similarity of 0.432; the average genetic similarity among the six other species was 0.729. The results from AFLP markers provided detailed estimates of the genetic variation within and among papaya cultivars, and supported the notion that C. papaya diverged from the rest of Carica species early in the evolution of this genus.

Carica↗
PubMed2003

Genetic identification of a female partial-sterile mutant in soybean.

We report here the genetic identification of a female partial-sterile mutant derived from soybean mutant L67-3483. L67-3483, which originated from the cultivar Clark after X-ray irradiation, is male and female fertile. All F1 plants in reciprocal pollinations of L67-3483 with 'Clark', 'Minsoy', or 'BSR 101' were female partial sterile. Partial sterility is expressed in the heterozygous condition at a single locus and upon self-pollination this locus exhibits a 1:1 segregation pattern. This locus is located on the terminus of the soybean molecular linkage group D1b+W, between simple sequence repeat (SSR) markers Satt157 and Satt266, and is linked to each by 5.3 and 1.2 cM, respectively. This gene is transmitted through both female and male gametes and there was no segregation distortion of SSR markers linked to this gene. We concluded that this female partial-sterile gene is a new mutation class, and differs from the previously reported mutation classes in soybean, i.e., sporophytic mutation, gametophytic female-specific mutation, and general gametophytic mutation. Restriction of recombination around the mutant gene suggested that this gene is located near or within (a) small inversion(s) or adjacent to (a) chromosomal deletion(s).

Chromosome Mapping↗
PubMed1997

Distribution of highly repeated DNA sequences in species of the genus Secale.

The presence and distribution of the most important highly repetitive DNA sequences of rye in cultivated and wild species of the genus Secale were investigated using fluorescence in situ hybridization. Accurate identification of individual chromosomes in the most commonly recognized species or subspecies of the genus Secale (S. cereale, S. ancestrale, S. segetale, S. afghanicum, S. dighoricum, S. montanum, S. montanum ssp. kuprijanovii, S. africanum, S. anatolicum, S. vavilovii, and S. silvestre) was achieved using three highly repetitive rye DNA sequences (probes pSc119.2, pSc74, and pSc34) and the 5S ribosomal DNA sequence pTa794. It is difficult to superimpose trends in the complexity of repetitive DNA during the evolution of the genus on conclusions from other cytogenetic and morphological assays. However, there are two clear groups. The first comprises the self-pollinated annuals S. silvestre and S. vavilovii that have few repeated nucleotide sequences of the main families of 120 and 480 bp. The second group presents amplification and interstitialization of the repeated nucleotide sequences and includes the perennials S. montanum, S. anatolicum, S. africanum, and S. kuprijanovii, as well as the annual and open-pollinated species S. cereale and its related weedy forms. The appearance of a new locus for 5S rRNA in S. cereale and S. ancestrale suggests that cultivated ryes evolved from this wild weedy species.

Biological Evolution↗
PubMed2001

Identification of barley genome segments introgressed into wheat using PCR markers.

Barley has several important traits that might be used in the genetic improvement of wheat. For this report, we have produced wheat-barley recombinants involving barley chromosomes 4 (4H) and 7 (5H). Wheat-barley disomic addition lines were crossed with 'Chinese Spring' wheat carrying the phlb mutation to promote homoeologous pairing. Selection was performed using polymerase chain reaction (PCR) markers to identify lines with the barley chromosome in the ph1b background. These lines were self pollinated, and recombinants were identified using sequence-tagged-site (STS) primer sets that allowed differentiation between barley and wheat chromosomes. Several recombinant lines were isolated that involved different STS-PCR markers. Recombination was confirmed by allowing the lines to self pollinate and rescreening the progeny via STS-PCR. Progeny testing confirmed 9 recombinants involving barley chromosome 4 (4H) and 11 recombinants involving barley chromosome 7 (5H). Some recombinants were observed cytologically to eliminate the possibility of broken chromosomes. Since transmission of the recombinant chromosomes was lower than expected and since seed set was reduced in recombinant lines, the utility of producing recombinants with this method is uncertain.

DNA, Plant↗
PubMed2002

How to be a fig wasp.

In the two decades since Janzen described how to be a fig, more than 200 papers have appeared on fig wasps (Agaonidae) and their host plants (Ficus spp., Moraceae). Fig pollination is now widely regarded as a model system for the study of coevolved mutualism, and earlier reviews have focused on the evolution of resource conflicts between pollinating fig wasps, their hosts, and their parasites. Fig wasps have also been a focus of research on sex ratio evolution, the evolution of virulence, coevolution, population genetics, host-parasitoid interactions, community ecology, historical biogeography, and conservation biology. This new synthesis of fig wasp research attempts to integrate recent contributions with the older literature and to promote research on diverse topics ranging from behavioral ecology to molecular evolution.

Animals↗
PubMed2004

Phylogeny and biology of neotropical orchid bees (Euglossini).

Orchid bees (Euglossini), noted for their brilliant iridescence, are elusive pollinators throughout the American tropics. Males are especially important in the pollination of some orchids, from which they collect aromatic fragrances thought to play a role in territorial display and courtship. The tribe contains approximately 190 described species divided among five genera, distributed from Mexico to central Argentina. Relatively intense study of their biology in the 1960s through the mid-1980s shed light on their nesting biology, chemical ecology, and classification. Vigorous taxonomic research led to the naming of many new species, revisions, and checklists, but phylogenetic studies were scarce. In the two decades following the last comprehensive review, phylogenetic research has resulted in new hypotheses of generic relationships, and further examination of male display has led to additional interpretations. Females in natural and artificial nesting cavities have revealed social interactions and additional details of parasitism within the nest. This review emphasizes areas in need of more study, particularly phylogeny, phylogeography, chemosensory ecology, and comparative behavior, and highlights how historical context can guide future research.

Animals↗
PubMed2004

Species specificity in pollen-pistil interactions.

For pollination to succeed, pollen must carry sperm through a variety of different floral tissues to access the ovules within the pistil. The pistil provides everything the pollen requires for success in this endeavor including distinct guidance cues and essential nutrients that allow the pollen tube to traverse enormous distances along a complex path to the unfertilized ovule. Although the pistil is a great facilitator of pollen function, it can also be viewed as an elaborate barrier that shields ovules from access from inappropriate pollen, such as pollen from other species. Each discrete step taken by pollen tubes en route to the ovules is a potential barrier point to ovule access and waste by inappropriate mates. In this review, we survey the current molecular understanding of how pollination proceeds, and ask to what extent is each step important for mate discrimination. As this field progresses, this synthesis of functional biology and evolutionary studies will provide insight into the molecular basis of the species barriers that maintain the enormous diversity seen in flowering plants.

Biological Evolution↗
PubMed2006

Airborne pollen concentrations and the incidence of allergic asthma and rhinoconjunctivitis in northern Italy from 1992 to 2003.

BACKGROUND: Aeroallergens and the environment play an important role in the pathogenesis of respiratory allergies. In a 12-year study carried out in Northern Italy (geographic area of Parma), the effects of airborne pollen and meteorological conditions on the incidence of allergic asthma and rhinoconjunctivitis were evaluated. PATIENTS AND METHODS: Among 9,060 subjects examined for respiratory pathologies at our Allergy Unit, Parma Hospital, Italy, from 1992 to 2003, only 1,054 positive to only one type of inhalant allergen in the skin prick test were studied, to avoid bias of cross-reactivity. Allergy and clinical aspects were compared with the duration of the pollination period, and peaks and total concentrations of airborne pollen. RESULTS: Our data showed a significantly growing trend of allergy to mites, pets and birch pollen and a significant increase in asthma, and a significantly decreasing trend of positive reactions to grasses and a decrease in rhinoconjunctivitis. At the same time, there was a significant decrease in total pollen counts, concentration peaks and pollination period of grasses. A significant increase was only observed in ragweed and ash-olive total and peak pollen concentrations. CONCLUSIONS: Significant correlations between the increasing incidence in asthma and allergy to mites, pets and birch pollen are shown. The decrease in the total pollen count and concentration peaks of grass pollen was correlated to the decreasing trend of rhinoconjunctivitis. The trend of increasing concentrations of ash-olive and ragweed pollen was not accompanied by an increase in the related allergy.

Adult↗
PubMed1976

Cycles of activity, group composition, and diet of Lemur mongoz mongoz Linnaeus 1766 in Madagascar.

A preliminary study of the ecology and behavior of Lemur mongoz mongoz was carried out in the northwest of Madagascar. The animals were observed for approximately 250 h in July till August, 1973, and for 50 h in June, 1974. L.m.mongoz has been reported to be diurnal and to live in groups of 6-8 individuals. However, we found the animals to be nocturnal and that groups contained an adult male, an adult female and their offspring (groups numbering from 2 to 4 individuals). L.m.mongoz is thus the only species of the genus Lemur studied to date that is active exclusively at night and that lives in family groups. L.m.mongoz was also found to have a very specialized diet. During our study, it was observed to feed on only five species of plant and mainly on the nectar-producing parts (flowers and nectaries) of four of these species. It spent most of its feeding time licking nectar from the flowers of the kapok tree, Ceiba pentandra, and is probably a major pollinator of this tree in Madagascar. In Africa and South and Central America, the kapok tree is usually bat-pollinated. A dietary preference for nectar, although common among bats, has not previously been observed in primates.

Animals↗
PubMed1973

Seasonal changes in IgE antibodies and their relationship to IgG antibodies during immunotherapy for ragweed hay fever.

Seasonal changes in IgE antibodies and their relationship to IgG antibodies were studied in 52 patients with ragweed hay fever and 10 normal controls. Allergic patients received either no immunotherapy, preseasonal immunotherapy, or high dose perennial immunotherapy with aqueous-mixed ragweed extract. Serums were collected before, during, just after, and 4 mo after the ragweed pollination season. IgE antibodies to ragweed antigen E (AgE) were measured using the radioallergosorbent test, and IgG antibodies were measured by radioimmunoprecipitation.IgE antibodies to AgE were elevated in all allergic patients, and rose during the ragweed pollination season. The magnitude of the rise in IgE antibody was a function of the preseasonal IgE antibody level. IgE antibody production in the treated groups was the same as in the untreated group when patients were matched on the basis of their preseasonal IgE antibody levels. Thus, we were not able to confirm previous reports that immunotherapy suppresses the seasonal rise in IgE antibodies. Furthermore, there was a close relationship between the levels of IgE and IgG antibodies in the high dose group. This finding is contrary to what one would expect were IgG antibodies acting to suppress the formation of IgE antibodies. Rather, it suggests that in certain patients either humoral immunological reactivity to ragweed antigens in the IgG and IgE classes is low to begin with or that this reactivity may wane after treatment with high doses of ragweed extract.

Adult↗
PubMed2006

Upregulation of a tonoplast-localized cytochrome P450 during petal senescence in Petunia inflata.

BACKGROUND: Gene expression in Petunia inflata petals undergoes major changes following compatible pollination. Severe flower wilting occurs reproducibly within 36 hours, providing an excellent model for investigation of petal senescence and programmed cell death. Expression of a number of genes and various enzyme activities involved in the degradation and remobilization of macromolecules have been found to be upregulated during the early stages of petal senescence. RESULTS: By performing differential display of cDNAs during Petunia inflata petal senescence, a highly upregulated gene encoding a cytochrome P450 was identified. Analysis of the complete cDNA sequence revealed that the predicted protein is a member of the CYP74C family (CYP74C9) and is highly similar to a tomato CYP74C allene oxide synthase (AOS) that is known to be active on 9-hydroperoxides. Cloning of the petunia genomic DNA revealed an intronless gene with a promoter region that carries signals found in stress-responsive genes and potential binding sites for Myb transcription factors. Transcripts were present at detectable levels in root and stem, but were 40 times more abundant in flowers 36 hours after pollination. Ethylene and jasmonate treatment resulted in transitory increases in expression in detached flowers. A protein fusion of the CYP74C coding region to a C-terminal GFP was found to be located in the tonoplast. CONCLUSION: Though oxylipins, particularly jasmonates, are known to be involved in stress responses, the role of other products of CYP74 enzymes is less well understood. The identification of a CYP74C family member as a highly upregulated gene during petal senescence suggests that additional products of fatty acid metabolism may play important roles during programmed cell death. In contrast to the chloroplast localization of AOS proteins in the CYP74A subfamily, GFP fusion data indicates that the petunia CYP74C9 enzyme is in the tonoplast. This result suggests that the highly similar CYP74C enzymes that have been identified in two other Solanaceous plants may also be associated with the vacuole, an organelle known to have a prominent role in programmed cell death.

Acetates↗
PubMed2004

Development of three different cell types is associated with the activity of a specific MYB transcription factor in the ventral petal of Antirrhinum majus flowers.

Petal tissue comprises several different cell types, which have specialised functions in pollination in different flowering plant species. In Antirrhinum majus, the MIXTA protein directs the formation of conical epidermal cells in petals. Transgenic experiments have indicated that MIXTA activity can also initiate trichome development, dependent on the developmental timing of its expression. MIXTA is normally expressed late in petal development and functions only in conical cell differentiation. However, an R2R3 MYB transcription factor very similar to MIXTA (AmMYBML1), which induces both trichome and conical cell formation in transgenic plants, is expressed very early during the development of the ventral petal. Its cellular expression pattern suggests that it fulfils three functions: trichome production in the corolla tube, conical cell development in the petal hinge epidermis and reinforcement of the hinge through differential mesophyll cell expansion. The DIVARICATA (DIV) gene is required for ventral petal identity. In div mutants, the ventral petal assumes the identity of lateral petals lacking these three specialised cell types, and expression of AmMYBML1 is significantly reduced compared with wild type, supporting the proposed role of AmMYBML1 in petal cell specification. We suggest that AmMYBML1 is regulated by DIV in association with the B-function proteins DEFICIENS and GLOBOSA, and, consequently, controls specification of particular cells within the ventral petal which adapt the corolla to specialised functions in pollination.

Alleles↗