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PubMed2006

Determination of traces of fipronil and its metabolites in pollen by liquid chromatography with electrospray ionization-tandem mass spectrometry.

Fipronil is a pesticide suspected of having harmful effects on honey bees at microgram per kilogram levels. Considering the lack of methodology, it thus appeared to be necessary to develop a method for the determination of the lowest amounts of fipronil and its metabolites in pollen. This paper describes a new analytical method with a limit of quantification (LOQ) of 0.1 microg/kg for a representative sample weight of 5 g. In the case of a field study, this tool was used for checking the possible existence of fipronil and/or metabolites in pollen samples, but none of them contained residues higher than the LOQ. This three-step rapid method uses liquid-solid solvent extraction with mechanical grinding, followed by liquid-liquid partitioning and Florisil solid-phase extraction for the two cleanup steps. The quantification is made by liquid chromatography with electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Indeed, combined with an adequate sample treatment, this technique offers good sensitivity and selectivity in such a complex matrix. The method has given good recoveries of 74-104% with relative standard deviations of 5.6-18.2%.

Chromatography, High Pressure Liquid↗
PubMed1997

Modulation of the allergic immune response in BALB/c mice by subcutaneous injection of high doses of the dominant T cell epitope from the major birch pollen allergen Bet v 1.

Several in vitro and in vivo studies indicate that application of high doses of dominant T cell epitopes can induce a state of antigen-specific non-responsiveness (anergy). In the present study, we developed a murine model of an allergic immune response to Bet v 1, the major birch pollen allergen. Mice were sensitized by injection of rBet v 1 and the allergic state was proven by the presence of allergen-specific IgE and positive immediate-type skin tests to Bet v 1. In epitope mapping experiments, an immunodominant T cell epitope of Bet v 1 in BALB/c mice was identified by the use of overlapping peptides. This peptide (BV 139) was subsequently employed for treatment. Two tolerization protocols were used: in one approach, the peptide was administered to naive mice before immunization (group BV139-S), in the second, already sensitized mice were treated (S-BV139). The results demonstrated that administering high doses of the dominant T cell epitope of Bet v 1 profoundly diminished T cell proliferation to the peptide in the BV139-S group, and to the peptide as well as to the whole protein in the S-BV139 group. Skin test reactivity to Bet v 1 was reduced in the BV139-S group. However, no differences in terms of specific antibody production between treated and untreated mice could be observed. This study provides evidence that administration of dominant T cell epitopes can down-regulate the allergen-specific T cell response. Proceeding on the assumption that the T lymphocyte response to allergens is crucial for the induction and maintenance of the allergic disease, a modulation of the immune response to allergens by treatment with T cell epitope peptides could represent a promising concept for immunotherapy in the future.

Adjuvants, Immunologic↗
PubMed2005

Adjuvant activity of pollen grains.

BACKGROUND: The induction of an immune response to a biologically inert soluble protein requires an adjuvant. Here we have examined whether intact grains of pollen display such adjuvant effect, accounting for the immunogenic activity of pollen protein allergens that are devoid of intrinsic pro-inflammatory/adjuvant property. METHODS: Human monocyte-derived dendritic cells (DCs) were cultured with intact grains of grass or ragweed pollen for 48 h. The state of DCs maturation was analyzed by FACS and their cytokine production by ELISA. T cell priming activity of DCs was examined in co-cultures with naïve cord blood-derived CD4(+) T cells. RESULTS: Contact with grains of pollen induced a distinct maturation program in immature DCs. Pollen up-regulated the expression of CD54, CD80, CD83, CD86, HLA-DR, CCR7, and CD40 on DCs. Moreover, CCR5 expression was up-regulated by pollen but suppressed by LPS. In sharp contrast to LPS-stimulated DCs, pollen-treated DCs did not produce cytokines [interleukin (IL)-10, IL-12, tumor necrosis factor (TNF)-alpha] but retained the ability to secrete high levels of these cytokines upon simulation with soluble CD40 ligand and interferon (IFN)-gamma. Pollen-primed DCs strongly stimulated the proliferation of allogeneic naïve CD4(+) T cells and promoted their development into effector cells producing high levels of IL-5 and IL-13 together with moderate levels of IFN-gamma and IL-4. CONCLUSION: Intact grains of pollen induce activation and maturation of DCs in vitro. Similar mechanisms may be effective in vivo, suggesting that pollen grain is not only an allergen carrier but also acts as an adjuvant in the induction phase of the allergic immune response.

Adjuvants, Immunologic↗
PubMed2005

Potential roles in rhinitis for protease and other enzymatic activities of allergens.

Exposure to airborne pollen, fungal allergens, and dust mite allergens is associated with the development of allergic rhinitis. Biologic function of allergens is considered to be a key determinant for allergenicity, and many clinically important allergens have been shown to possess enzymatic activity. It is proposed that by enabling allergens to breach the integrity of the airway epithelial barrier, proteolytic activity plays an adjuvant pro-allergic role influencing immunogenicity. In this review, current evidence regarding enzymatic activity of aeroallergens is described, and the potential role of aeroallergens in allergic rhinitis is discussed.

Allergens↗
PubMed1978

Potential of plant genetic systems for monitoring and screening mutagens.

Plants have too long been ignored as useful screening and monitoring systems of environmental mutagens. However, there are about a dozen reliable, some even unique, plant genetic systems that can increase the scope and effectiveness of chemical and physical mutagen screening and monitoring procedures. Some of these should be included in the Tier II tests. Moreover, plants are the only systems now in use as monitors of genetic effects caused by polluted atmosphere and water and by pesticides. There are several major advantages of the plant test systems which relate to their reproductive nature, easy culture and growth habits that should be considered in mutagen screening and monitoring. In addition to these advantages, the major plant test systems exhibit numerous genetic and chromosome changes for determining the effects of mutagens. Some of these have not yet been detected in other nonmammalian and mammalian test systems, but probably occur in the human organism. Plants have played major roles in various aspects of mutagenesis research, primarily in mutagen screening (detection and verification of mutagenic activity), mutagen monitoring, and determining mutagen effects and mechanisms of mutagen action. They have played lesser roles in quantification of mutagenic activity and understanding the nature of induced mutations.Mutagen monitoring with plants, especially in situ on land or in water, will help determine potential genetic hazards of air and water pollutants and protect the genetic purity of crop plants and the purity of the food supply. The Tradescantia stamen-hair system is used in a mobile laboratory for determining the genetic effects of industrial and automobile pollution in a number of sites in the U.S.A. The fern is employed for monitoring genetic effects of water pollution in the Eastern states. The maize pollen system and certain weeds have monitored genetic effects of pesticides. Several other systems that have considerable value and should be developed and more widely used in mutagen monitoring and screening, especially for in situ monitoring, are discussed. Emphasis is placed on pollen systems in which changes in pollen structure, chemistry, and chromosomes can be scored for monitoring; and screening systems which can record low levels of genetic effects as well as provide information on the nature of induced mutations. THE VALUE OF PLANT SYSTEMS FOR MONITORING AND SCREENING MUTAGENS CAN BE IMPROVED BY: greater knowledge of plant cell processes at the molecular and ultrastructural levels; relating these processes to mutagen effects and plant cell responses; improving current systems for increased sensitivity, ease of detecting genetic and chromosome changes, recording of data (including automation), and for extending the range of genetic and chromosome end points; and designing and developing new systems with the aid of previous and current botanical and genetic knowledge.

Biological Assay↗
PubMed2003

[The immunological parameters and risk factors for pollen-induced allergic rhinitis and asthma].

UNLABELLED: Naturally occurring exposure to pollen allergens causes symptoms of allergic rhinitis, conjunctivitis and asthma in susceptible individuals. It is, however, unknown why some subjects develop only an allergic rhinitis while others develop asthma as well. The aim of this study was to investigate the difference of immunological parameters in patients with pollen-induced seasonal allergic rhinitis (SAR) and asthma and to determine the risk factors for pollinosis with asthma. We evaluated the demographic and clinical characteristics of the patients, sensitisation pattern to tree-, grass- and weed-pollen and perennial inhalant allergens according to skin prick tests, allergic inflammation parameters (blood and nasal eosinophil count, serum IgE, eosinophil cationic protein levels) in and out of the pollinosis season. Logistic regression analysis was used to rate the effect of covariates on risk for pollinosis and asthma. One hundred and one patients (52 men and 49 women) aged 16-63 years (median 24 yrs.) with pollinosis symptoms were investigated. All patients suffered from moderate-severe seasonal allergic rhinitis, 96% from concomitant allergic conjunctivitis, 23.8% had seasonal asthma. The significant clinical and demographic risk factors for pollinosis with asthma were smoking (OR=15.4, p=0.003) and pollinosis season lasting more than 14 weeks (OR=5.6, p=0.02). The patients with seasonal allergic rhinitis alone were significantly more frequently sensitized to orchard grass (p=0.005), ragweed (p=0.02), lamb's quarter (p=0.05) allergens. During the season the blood eosinophil count raised in all patients (p<0.01). It was shown statistically that there were no differences between groups in blood and nasal eosinophil count, serum eosinophil cationic protein level. The patients with seasonal allergic rhinitis and asthma had higher levels of serum IgE during the season (p=0.05) and out of it (p=0.01). More than two times elevated serum IgE in acute and symptom-free period of pollinosis was considered as a significant risk factor for pollinosis with asthma (OR=3.5, p=0.04 and OR=3.4, p=0.03). CONCLUSIONS: Pollinosis presented with seasonal asthma in 23.8% of cases. Our data indicate that patients with seasonal allergic rhinitis and asthma differ from the patients with seasonal allergic rhinitis alone according to higher serum IgE levels. Prolonged pollinosis season, smoking and high IgE levels increase the risk for seasonal asthma in pollen-induced allergic rhinitis subjects.

Adolescent↗
PubMedDate not supplied

The perennial pattern of clinical symptoms in children monosensitized to Olea europaea pollen allergens in comparison with subjects with Parietaria and Gramineae pollinosis.

Because the pediatric age represents a good model to study the correlation between the exposure to allergens and development of respiratory allergy, we investigated the occurrence of a perennial type of symptomatology in children monosensitized to Olea europaea (O.e.) pollen allergens compared with subjects with monosensitization to Parietaria (P) and Gramineae (G) in order to confirm our previous observations in adults. We selected a group of 52 children with rhinitis and/or bronchial asthma and a SPT positivity only to pollens (30 to P, 15 to G, and 7 to O.e.). Using commercially available allergenic extracts and reagents, the following diagnostic procedures were performed: skin prick test (SPT), specific IgE assays (RAST), nonspecific bronchial provocation test (NsBPT) and specific nasal provocation test (sNPT), respectively, in patients with bronchial asthma and rhinitis. Pollen counts and a statistical analysis using Spearman's correlation test were also carried out. Six of seven children with monosensitization to O.e. allergens showed a perennial pattern of symptoms in comparison to 7 of 23 and 3 of 12, respectively, in subjects with P and G pollinosis. All patients with perennial nasal symptoms of O.e. group exhibited a late nasal response after sNPT. Although these findings on nasal response may partially explain the occurrence of a prolonged inflammation of the nose induced by O.e. allergens, we think that other possibilities could be investigated. In our opinion, further studies are necessary using better purified and standardized diagnostic materials and, moreover, a greater number of O.e. monosensitized children living in other geographical areas need to be examined for a comparison of our results with theirs.

Adolescent↗
PubMed2007

Functional analysis of birch pollen allergen Bet v 1-specific regulatory T cells.

Allergen-specific immunotherapy using peptides is an efficient treatment for allergic diseases. Recent studies suggest that the induction of CD4+ regulatory T (Treg) cells might be associated with the suppression of allergic responses in patients after allergen-specific immunotherapy. Our aim was to identify MHC class II promiscuous T cell epitopes for the birch pollen allergen Bet v 1 capable of stimulating Treg cells with the purpose of inhibiting allergic responses. Ag-reactive CD4+ T cell clones were generated from patients with birch pollen allergy and healthy volunteers by in vitro vaccination of PBMC using Bet v 1 synthetic peptides. Several CD4+ T cell clones were induced by using 2 synthetic peptides (Bet v 1(141-156) and Bet v 1(51-68)). Peptide-reactive CD4+ T cells recognized recombinant Bet v 1 protein, indicating that these peptides are produced by the MHC class II Ag processing pathway. Peptide Bet v 1(141-156) appears to be a highly MHC promiscuous epitope since T cell responses restricted by numerous MHC class II molecules (DR4, DR9, DR11, DR15, and DR53) were observed. Two of these clones functioned as typical Treg cells (expressed CD25, GITR, and Foxp3 and suppressed the proliferation and IL-2 secretion of other CD4+ T cells). Notably, the suppressive activity of these Treg cells required cell-cell contact and was not mediated through soluble IL-10 or TGF-beta. The identified promiscuous MHC class II epitope capable of inducing suppressive Treg responses may have important implication for the development of peptide-based Ag-specific immunotherapy to birch pollen allergy.

Allergens↗
PubMed2004

Effect of a low dose of aluminum on mitotic and meiotic activity, 4C DNA content, and pollen sterility in rice, Oryza sativa L. cv. Lalat.

Aluminum toxicity in acidic soils poses a major threat to plant growth and development. The effects of a low dose of aluminum (50 microM, AlCl3) on various cytological parameters, including mitotic and meiotic chromosomal divisions, in situ nuclear DNA content, interphase nuclear volume (INV), and pollen fertility were compared in untreated (controls) and treated rice plants (Oryza sativa cv. Lalat). The results showed varied chromosomal abnormalities, including chromosome stickiness, laggards, sticky bridge, occurrence of micronuclei, as well as binucleate and multinucleated cells, as a result of aluminum treatment. Aluminum toxicity also inhibited to a small extent the growth of the rice cultivar Lalat. The mitotic and meiotic indexes, even after a prolonged period of recovery, were significantly low. The chromosomal anomalies in the meiotic cells persisted, and plants exhibited a high percentage of pollen sterility (approximately 64%). The nuclear DNA content declined markedly from 11.85 pg in the control to 6.30 pg in the treated plants. The INV also varied significantly between the untreated (controls) and the treated plants. The occurrences of different types of chromosomal aberrations, reduction in the amount of nuclear DNA, and persistence of the phytotoxic effects at the post-treatment stage suggest carcinogenic effects of aluminum on rice plants. The presence of aluminum in acidic soils might thus be extremely hazardous and might cause permanent cytotoxic disorder in rice plants.

Aluminum Chloride↗
PubMed1982

Cross-reactivity between Acacia (wattle) and rye grass pollen allergens. Detection of allergens in Acacia (wattle) pollen.

Immunoglobulin E (IgE), directed against components of Acacia (wattle) pollen, has been detected by radioallergosorbent tests (RAST) in the sera of some children and adults who develop allergic symptoms in the presence of flowering Acacia trees in Australia. All these subjects also had high levels of IgE directed against Lolium perenne (rye grass) pollen. Inhibition by RAST showed that most of the IgE molecules which bound to Acacia pollen components also bound to L. perenne pollen extracts, and to Glycoprotein 1, the major allergen of L. perenne pollen. In these assays, the allergens have been immobilized on polyvinyl chloride microtitre trays: the sensitivity of this approach is compared to that of commercial RAST kits.

Acacia↗
PubMedDate not supplied

Thunderstorm-associated asthma or shortness of breath epidemic: a Canadian case report.

Thunderstorm-associated asthma epidemics have been documented in the literature, but no Canadian experience has been reported. On July 31, 2000, a thunderstorm-associated epidemic of asthma or shortness of breath occurred in Calgary, Alberta. The Calgary Health Region investigated the event using diagnostic data from emergency departments, an urgent care medical clinic and patient interviews, in addition to bioaerosol counts, pollutant data and weather data reflecting atmospheric conditions at that time. On July 31, 2000 and August 1, 2000, 157 people sought care for asthma symptoms. The expected number of people to seek care for such symptoms in a 48 h period in Calgary is 17. Individuals with a personal or family history of asthma, allergies or hay fever who were not taking regular medication for these conditions and who were outdoors before the storm appeared to have been preferentially affected. A stagnant air mass the day before the thunderstorm may have resulted in declining bioaerosol concentrations, and the possible accumulation of spore and pollen reservoirs within mould and plant structures. The elevated bioaerosol concentrations observed on the day of the thunderstorm may be attributed to the sudden onset of high winds during the thunderstorm, which triggered a sudden release of spores and pollens into the atmosphere, which was probably responsible for the epidemic. Several pollutant levels slightly increased on the day of the storm and possibly also played a role in symptom development. It is unclear whether an atmospheric pressure drop contributed to the release of spores and pollens.

Adolescent↗
PubMed1999

[Short-term immunotherapy--a survey of current studies].

Immunotherapy (IT) plays a central role in the therapy of allergic rhinitis as it was proved to be causal and preventive. IT induces humoral and cellular changes in the immune system, a reduction of symptoms and a prophylactic effect regarding a possible expansion of the allergene spectrum and of involved organ systems. Regular therapeutic schedules include allergen injections starting immediately after the pollen season and ending just before the expected beginning of a season. Additionally, perseasonal and perennial therapy schemes have been used. In all these, a phase of dose-increase is followed by an individually adjusted steady-state preservation-phase. In perseasonal and perennial scheme the injections are given during the pollen season. The preseasonal shortterm-immunotherapy is another schedule. The increase of the injected allergen-dose is made very fast (most commonly during seven weeks), so that the phase of dose-increase is shortened considerably, and a preservation-phase does not take place. This shortterm-immunotherapy has been developed for patients who consult their doctor shortly before the start of the pollen season. The preseasonal shortterm-immunotherapy has been shown to be efficient regarding allergic rhinitis caused by grass-, rye-, birch-, hazel- and alder-pollen. Clinical and experimental data of two placebo-controlled trials and one open study are presented and the role of this new immunotherapy approach is discussed.

Adult↗
PubMed2005

Role of auxin in regulating Arabidopsis flower development.

To elucidate the role of auxin in flower morphogenesis, its distribution patterns were studied during flower development in Arabidopsis thaliana (L.) Heynh. Expression of DR5::GUS was regarded to reflect sites of free auxin, while immunolocalization with auxin polyclonal antibodies visualized conjugated auxin distribution. The youngest flower bud was loaded with conjugated auxin. During development, the apparent concentration of free auxin increased in gradual patterns starting at the floral-organ tip. Anthers are major sites of high concentrations of free auxin that retard the development of neighboring floral organs in both the acropetal and basipetal directions. The IAA-producing anthers synchronize flower development by retarding petal development and nectary gland activity almost up to anthesis. Tapetum cells of young anthers contain free IAA which accumulates in pollen grains, suggesting that auxin promotes pollen-tube growth towards the ovules. High amounts of free auxin in the stigma induce a wide xylem fan immediately beneath it. After fertilization, the developing embryos and seeds show elevated concentrations of auxin, which establish their axial polarity. This developmental pattern of auxin production during floral-bud development suggests that young organs which produce high concentrations of free IAA inhibit or retard organ-primordium initiation and development at the shoot tip.

Arabidopsis↗
PubMed2003

Spinosad toxicity to pollinators and associated risk.

Spinosad is a natural insecticide derived from an actinomycete bacterium species, Saccharopolyspora spinosa (Mertz and Yao 1990), that displays the efficacy of a synthetic insecticide. It consists of the two most active metabolites, designated spinosyn A and D. Both spinosyns are readily degraded in moist aerobic soil, and field dissipation, which is quite rapid (half-life, 0.3-0.5 d) can be attributed to photolysis or a combination of metabolism and photolysis. Spinosad causes neurological effects in insects that are consistent with the general activation of nicotinic acetylcholine receptors but by a mechanism that is novel among known insecticide compounds. Spinosad has a high level of efficacy for lepidopteran larvae, as well as some Diptera, Coleoptera, Thysanoptera, and Hymenoptera, but has limited to no activity to other insects and exhibits low toxicity to mammals and other wildlife. Although spinosad has low toxicity to most beneficial insects, initial acute laboratory tests indicated that spinosad is intrinsically toxic to pollinators. The hazard of spinosad to bees was evaluated using a tiered approach. Initial acute laboratory exposures were conducted, followed by toxicity of residues of spinosad on treated foliage, greenhouse studies to assess acute as well as chronic toxicity, confined field assessments, and finally full field studies using a variety of crops under typical use conditions. These data were used to assess the potential of adverse effects on foraging bees following the use of spinosad. This research has clearly demonstrated that spinosad residues that have been allowed to dry for 3 hr are not acutely harmful to honeybees when low-volume and ultralow-volume sprays are used. Further, glasshouse and semifield studies have demonstrated that dried residues are not acutely toxic, and although pollen and nectar from sprayed plants may have transient effects on brood development, the residues do not overtly affect hive viability of either the honeybee or the bumblebee. Field studies in which typical application methods of spinosad were used on a variety of crops have demonstrated that spinosad has low risk to adult honeybees and has little or no effect on hive activity and brood development. The collective evidence from these studies indicates that once spinosad residues have dried on plant foliage, generally 3 hr or less, the risk of spinosad to honeybees is negligible.

Agriculture↗
PubMed2001

Impact of Bt corn pollen on monarch butterfly populations: a risk assessment.

A collaborative research effort by scientists in several states and in Canada has produced information to develop a formal risk assessment of the impact of Bt corn on monarch butterfly (Danaus plexippus) populations. Information was sought on the acute toxic effects of Bt corn pollen and the degree to which monarch larvae would be exposed to toxic amounts of Bt pollen on its host plant, the common milkweed, Asclepias syriaca, found in and around cornfields. Expression of Cry proteins, the active toxicant found in Bt corn tissues, differed among hybrids, and especially so in the concentrations found in pollen of different events. In most commercial hybrids, Bt expression in pollen is low, and laboratory and field studies show no acute toxic effects at any pollen density that would be encountered in the field. Other factors mitigating exposure of larvae include the variable and limited overlap between pollen shed and larval activity periods, the fact that only a portion of the monarch population utilizes milkweed stands in and near cornfields, and the current adoption rate of Bt corn at 19% of North American corn-growing areas. This 2-year study suggests that the impact of Bt corn pollen from current commercial hybrids on monarch butterfly populations is negligible.

Animals↗
PubMed2006

AFLP and PCR-based markers linked to Rf3, a fertility restorer gene for S cytoplasmic male sterility in maize.

The Rf3 gene restores the pollen fertility disturbed by S male sterile cytoplasm. In order to develop molecular markers tightly linked to Rf3, we used amplified fragment length polymorphism (AFLP) technique with near isogenic lines (NILs) and bulk segregant analysis (BSA). A BC(1)F(1) population from a pair of NILs with different Rf3 locus was constructed and 528 primer combinations was screened. A linkage map was constructed around the Rf3 locus, which was mapped on the distal region of chromosome 2 long arm with the help of SSR marker UMC2184. The closest marker E7P6 was 0.9 cM away from Rf3. Marker E3P1, 2.4 cM from Rf3, and E12M7, 1.8 cM from Rf3, were converted into a codominant CAPS and a dominant SCAR marker, and designated as CAPSE3P1 and SCARE12M7, respectively. These markers are useful for marker-assisted selection and map-based cloning of the Rf3 gene.

Chromosome Mapping↗
PubMed2004

Grain yields with limited water.

Plant reproduction is sensitive to water deficits, especially during the early phases when development may cease irreversibly even though the parent remains alive. Grain numbers decrease because of several developmental changes, especially ovary abortion in maize (Zea mays L.) or pollen sterility in small grains. In maize, the water deficits inhibit photosynthesis, and the decrease in photosynthate flux to the developing organs appears to trigger abortion. Abscisic acid also increases in the parent and may play a role, perhaps by inhibiting photosynthesis through stomatal closure. Recent work indicates that invertase activity is inhibited and starch is diminished in the ovaries or affected pollen. Also, sucrose fed to the stems rescues many of the ovaries otherwise destined to abort. The feeding restores some of the ovary starch and invertase activity. These studies implicate invertase as a limiting enzyme step for grain yields during a water deficit, and transcript profiling with microarrays has identified genes that are up- or down-regulated during water deficit-induced abortion in maize. However, profiling studies to date have not reported changes in invertase or starch synthesizing genes in water-deficient ovaries, perhaps because there were too few sampling times. The ovary rescue with sucrose feeding indicates either that the changes identified in the profiling are of no consequence for inhibiting ovary development or that gene expression reverts to control levels when the sugar stream recovers. Careful documentation of tissue- and developmentally specific gene expression are needed to resolve these issues and link metabolic changes to the decreased sugar flux affecting the reproductive organs.

Agriculture↗
PubMed2002

Embryo and endosperm development is disrupted in the female gametophytic capulet mutants of Arabidopsis.

The female gametophyte of higher plants gives rise, by double fertilization, to the diploid embryo and triploid endosperm, which develop in concert to produce the mature seed. What roles gametophytic maternal factors play in this process is not clear. The female-gametophytic effects on embryo and endosperm development in the Arabidopsis mea, fis, and fie mutants appear to be due to gametic imprinting that can be suppressed by METHYL TRANSFERASE1 antisense (MET1 a/s) transgene expression or by mutation of the DECREASE IN DNA METHYLATION1 (DDM1) gene. Here we describe two novel gametophytic maternal-effect mutants, capulet1 (cap1) and capulet2 (cap2). In the cap1 mutant, both embryo and endosperm development are arrested at early stages. In the cap2 mutant, endosperm development is blocked at very early stages, whereas embryos can develop to the early heart stage. The cap mutant phenotypes were not rescued by wild-type pollen nor by pollen from tetraploid plants. Furthermore, removal of silencing barriers from the paternal genome by MET1 a/s transgene expression or by the ddm1 mutation also failed to restore seed development in the cap mutants. Neither cap1 nor cap2 displayed autonomous seed development, in contrast to mea, fis, and fie mutants. In addition, cap2 was epistatic to fis1 in both autonomous endosperm and sexual development. Finally, both cap1 and cap2 mutant endosperms, like wild-type endosperms, expressed the paternally inactive endosperm-specific FIS2 promoter GUS fusion transgene only when the transgene was introduced via the embryo sac, indicating that imprinting was not affected. Our results suggest that the CAP genes represent novel maternal functions supplied by the female gametophyte that are required for embryo and endosperm development.

Arabidopsis↗