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PubMed1992

Role of Abscisic Acid in the Induction of Desiccation Tolerance in Developing Seeds of Arabidopsis thaliana.

In contrast to wild-type seeds of Arabidopsis thaliana and to seeds deficient in (aba) or insensitive to (abi3) abscisic acid (ABA), maturing seeds of recombinant (aba,abi3) plants fail to desiccate, remain green, and lose viability upon drying. These double-mutant seeds acquire only low levels of the major storage proteins and are deficient in several low mol wt polypeptides, both soluble and bound, and some of which are heat stable. A major heat-stable glycoprotein of more than 100 kilodaltons behaves similarly; during seed development, it shows a decrease in size associated with the abi3 mutation. In seeds of the double mutant from 14 to 20 days after pollination, the low amounts of various maturation-specific proteins disappear and many higher mol wt proteins similar to those occurring during germination are induced, but no visible germination is apparent. It appears that in the aba,abi3 double mutant seed development is not completed and the program for seed germination is initiated prematurely in the absence of substances protective against dehydration. Seeds may be made desiccation tolerant by watering the plants with the ABA analog LAB 173711 or by imbibition of isolated immature seeds, 11 to 15 days after pollination, with ABA and sucrose. Whereas sucrose stimulates germination and may protect dehydration-sensitive structures from desiccation damage, ABA inhibits precocious germination and is required to complete the program for seed maturation and the associated development of desiccation tolerance.

Journal Article↗
PubMed2003

Biosynthesis and emission of terpenoid volatiles from Arabidopsis flowers.

Arabidopsis is believed to be mostly self-pollinated, although several lines of genetic and morphological evidence indicate that insect-mediated outcrossing occurs with at least a low frequency in wild populations. Here, we show that Arabidopsis flowers emit both monoterpenes and sesquiterpenes, potential olfactory cues for pollinating insects. Of the 32 terpene synthase genes in the Arabidopsis genome, 20 were found to be expressed in flowers, 6 of these exclusively or almost exclusively so. Two terpene synthase genes expressed exclusively in the flowers and one terpene synthase gene expressed almost exclusively in the flowers were characterized and found to encode proteins that catalyze the formation of major floral volatiles. A beta-glucuronidase fusion construct with a promoter of one of these genes demonstrated that gene expression was restricted to the sepals, stigmas, anther filaments, and receptacles, reaching a peak when the stigma was receptive to cross pollen. The observation that Arabidopsis flowers synthesize and emit volatiles raises intriguing questions about the reproductive behavior of Arabidopsis in the wild and allows detailed investigations of floral volatile biosynthesis and its regulation to be performed with this model plant system.

Alkyl and Aryl Transferases↗
PubMed2004

The F-box protein AhSLF-S2 controls the pollen function of S-RNase-based self-incompatibility.

Recently, we have provided evidence that the polymorphic self-incompatibility (S) locus-encoded F-box (SLF) protein AhSLF-S(2) plays a role in mediating a selective S-RNase destruction during the self-incompatible response in Antirrhinum hispanicum. To investigate its role further, we first transformed a transformation-competent artificial chromosome clone (TAC26) containing both AhSLF-S(2) and AhS(2)-RNase into a self-incompatible (SI) line of Petunia hybrida. Molecular analyses showed that both genes are correctly expressed in pollen and pistil in four independent transgenic lines of petunia. Pollination tests indicated that all four lines became self-compatible because of the specific loss of the pollen function of SI. This alteration was transmitted stably into the T1 progeny. We then transformed AhSLF-S(2) cDNA under the control of a tomato (Lycopersicon esculentum) pollen-specific promoter LAT52 into the self-incompatible petunia line. Molecular studies revealed that AhSLF-S(2) is specifically expressed in pollen of five independent transgenic plants. Pollination tests showed that they also had lost the pollen function of SI. Importantly, expression of endogenous SLF or SLF-like genes was not altered in these transgenic plants. These results phenocopy a well-known phenomenon called competitive interaction whereby the presence of two different pollen S alleles within pollen leads to the breakdown of the pollen function of SI in several solanaceaous species. Furthermore, we demonstrated that AhSLF-S(2) physically interacts with PhS(3)-RNase from the P. hybrida line used for transformation. Together with the recent demonstration of PiSLF as the pollen determinant in P. inflata, these results provide direct evidence that the polymorphic SLF including AhSLF-S(2) controls the pollen function of S-RNase-based self-incompatibility.

Amino Acid Sequence↗
PubMed2005

ODORANT1 regulates fragrance biosynthesis in petunia flowers.

Floral scent is important to plant reproduction because it attracts pollinators to the sexual organs. Therefore, volatile emission is usually tuned to the foraging activity of the pollinators. In Petunia hybrida, volatile benzenoids determine the floral aroma. Although the pathways for benzenoid biosynthesis have been characterized, the enzymes involved are less well understood. How production and emission are regulated is unknown. By targeted transcriptome analyses, we identified ODORANT1 (ODO1), a member of the R2R3-type MYB family, as a candidate for the regulation of volatile benzenoids in Petunia hybrida cv W115 (Mitchell) flowers. These flowers are only fragrant in the evening and at night. Transcript levels of ODO1 increased before the onset of volatile emission and decreased when volatile emission declined. Downregulation of ODO1 in transgenic P. hybrida Mitchell plants strongly reduced volatile benzenoid levels through decreased synthesis of precursors from the shikimate pathway. The transcript levels of several genes in this pathway were reduced by suppression of ODO1 expression. Moreover, ODO1 could activate the promoter of the 5-enol-pyruvylshikimate-3-phosphate synthase gene. Flower pigmentation, which is furnished from the same shikimate precursors, was not influenced because color and scent biosynthesis occur at different developmental stages. Our studies identify ODO1 as a key regulator of floral scent biosynthesis.

Amino Acid Sequence↗
PubMed1999

Molecular analysis of the anthocyanin2 gene of petunia and its role in the evolution of flower color.

The shape and color of flowers are important for plant reproduction because they attract pollinators such as insects and birds. Therefore, it is thought that alterations in these traits may result in the attraction of different pollinators, genetic isolation, and ultimately, (sympatric) speciation. Petunia integrifolia and P. axillaris bear flowers with different shapes and colors that appear to be visited by different insects. The anthocyanin2 (an2) locus, a regulator of the anthocyanin biosynthetic pathway, is the main determinant of color differences. Here, we report an analysis of molecular events at the an2 locus that occur during Petunia spp evolution. We isolated an2 by transposon tagging and found that it encodes a MYB domain protein, indicating that it is a transcription factor. Analysis of P. axillaris subspecies with white flowers showed that they contain an2(-) alleles with two alternative frameshifts at one site, apparently caused by the insertion and subsequent excision of a transposon. A third an2(-) allele has a nonsense mutation elsewhere, indicating that it arose independently. The distribution of polymorphisms in an2(-) alleles suggests that the loss of an2 function and the consequent changes in floral color were not the primary cause for genetic separation of P. integrifolia and P. axillaris. Rather, they were events that occurred late in the speciation process, possibly to reinforce genetic isolation and complete speciation.

Alleles↗
PubMed2000

Developmental regulation of methyl benzoate biosynthesis and emission in snapdragon flowers.

In snapdragon flowers, the volatile ester methyl benzoate is the most abundant scent compound. It is synthesized by and emitted from only the upper and lower lobes of petals, where pollinators (bumblebees) come in contact with the flower. Emission of methyl benzoate occurs in a rhythmic manner, with maximum emission during the day, which correlates with pollinator activity. A novel S-adenosyl-l-methionine:benzoic acid carboxyl methyl transferase (BAMT), the final enzyme in the biosynthesis of methyl benzoate, and its corresponding cDNA have been isolated and characterized. The complete amino acid sequence of the BAMT protein has only low levels of sequence similarity to other previously characterized proteins, including plant O-methyl transferases. During the life span of the flower, the levels of methyl benzoate emission, BAMT activity, BAMT gene expression, and the amounts of BAMT protein and benzoic acid are developmentally and differentially regulated. Linear regression analysis revealed that production of methyl benzoate is regulated by the amount of benzoic acid and the amount of BAMT protein, which in turn is regulated at the transcriptional level.

Amino Acid Sequence↗
PubMed2000

Overexpression of a gene encoding a cytochrome P450, CYP78A9, induces large and seedless fruit in arabidopsis.

An activation tagging screen in which the cauliflower mosaic virus 35S enhancer was inserted randomly into an Arabidopsis genome homozygous for the floral homeotic mutation apetala2-1 (ap2-1) resulted in a line (28-5) with extraordinarily wide, heart-shaped ovaries. The ovary of the 28-5 ap2-1 mutant shows an oval shape because of increased numbers of enlarged cells. When the ap2-1 mutation is crossed out of the genetic background, more elongated rather than wider fruits are obtained. Normally, Arabidopsis fruits will develop to a normal size only when the ovules are present and fertilized. In the 28-5 single mutant, the siliques keep growing despite failure of fertilization and can reach nearly normal size. When wild-type pollen was used to pollinate the mutant pistil, the pollinated 28-5 silique became >10% longer and 40% wider than a wild-type silique, although producing very few seeds. The enhancer insertion in line 28-5 acts by hyperactivating a cytochrome P450 gene, CYP78A9. The pistil of 28-5 ap2-1 mutant flowers shows a structure similar to that of Capsella bursa-pastoris, a distant mustard relative of Arabidopsis, suggesting that the processes regulated by the CYP78A9-encoded protein may be involved in evolutionary control of carpel shape.

Arabidopsis↗
PubMed1992

A maize embryo-specific gene encodes a proline-rich and hydrophobic protein.

A gene from maize that encodes a hybrid proline-rich protein (HyPRP) formed by two well-defined domains, proline-rich and hydrophobic, respectively, has been characterized at the level of its structure and expression. The proline-rich domain is composed of elements PPYV and PPTPRPS, similar to those found in PRP proteins from soybean. The hydrophobic domain is rich in cysteine and is similar to seed proteins, mainly to a soybean hydrophobic seed protein. In maize, HyPRP is encoded by a single gene, and its mRNA accumulates in immature maize zygotic embryos, with a maximum accumulation between 12 and 18 days after pollination. The HyPRP mRNA can also be detected in ovary prior to pollination. In situ hybridization experiments on embryo sections show an expression of the gene in scutellum and in nonvascular cells from the embryo axis. Functional hypotheses related to HyPRP are discussed.

Amino Acid Sequence↗
PubMed2003

Balancing population size and genetic information in parentage analysis studies.

In parentage analysis studies, the parameters of interest typically are not the parent assignments themselves, but population parameters such as variance in fertility, self-pollination rate, or average dispersal distances. The precision of parameter estimates is affected by two factors: the number of offspring under consideration, and the precision with which the offspring can be assigned to parents. When assignment of parents is based on genetic information, the confidence in assignments is affected by the number and polymorphism of the loci considered, and by the number of potential parents in the population. Studying larger populations may yield higher numbers of offspring, but since larger populations contain more potential parents, more (or more highly polymorphic) loci are necessary to attain a given level of confidence in the parent assignments. This article addresses how to relate the size of the population and the number of loci when designing a study. It is shown that the number of loci needed to assign all offspring unambiguously is proportional to the logarithm of the population size. In some cases, the constant of proportionality can be determined, eliminating the need for simulation-based projections. Population-wide measures of uncertainty in parent assignments are also introduced, and it is shown that holding uncertainty "steady" as the population size increases also requires increasing the number of loci proportional to the logarithm of the population size. Data from a study of self-pollination are used to illustrate the techniques suggested.

Biometry↗
PubMed2000

Exploring the genetic basis and proximate causes of female fertility advantage in gynodioecious Thymus vulgaris.

In many gynodioecous species, females produce more viable seeds than hermaphrodites. Knowledge of the relative contribution of inbreeding depression in hermaphrodites and maternal sex effects to the female fertility advantage and the genetic basis of variation in female fertility advantage is central to our understanding of the evolution of gender specialization. In this study we examine the relative contribution of inbreeding and maternal sex to the female fertility advantage in gynodioecious Thymus vulgaris and quantify whether there is genetically based variation in female fertility advantage for plants from four populations. Following controlled self and outcross (sib, within-population, and between-population) pollination, females had a more than twofold fertility advantage (based on the number of germinating seeds per fruit), regardless of the population of origin and the type of pollination. Inbreeding depression on viable seed production by hermaphrodites occurred in two populations, where inbreeding had been previously detected. Biparental inbreeding depression on viable seed production occurred in three of four populations for females, but in only one population for hermaphrodites. Whereas the maternal sex effect may consistently enhance female fertility advantage, inbreeding effects may be limited to particular population contexts where inbreeding may occur. A significant family x maternal sex interaction effect on viable seed production was observed, illustrating that the extent of female fertility advantage varies significantly among families. This result is due to greater variation in hermaphrodite (relative to female) seed fertility between families. Despite this genetic variation in female fertility advantage and the highly female biased sex ratios in populations of T. vulgaris, gynodioecy is a stable polymorphism, suggesting that strong genetic and/or ecological constraints influence the stability of this polymorphism.

Analysis of Variance↗
PubMed2000

Pollen discounting and the evolution of selfing in Arenaria uniflora (caryophyllaceae).

Although most models of mating system evolution assign a central role to the male transmission advantage of selfing genotypes, empirical data on the male fitness consequences of increased self-pollination are still uncommon. Here, I use measures of pollen import and export by focal plants in genotyped arrays to investigate the effects of floral morphology and pollination environment on self and outcross male function. Plants from an autogamous population of Arenaria uniflora (Caryophyllaceae) exhibit complete pollen discounting relative to closely related outcrossers, as do morphologically intermediate F1 hybrids between the two populations. However, the low cumulative male fitness of hybrids probably results from reduced pollen number or competitive ability, rather than a nonlinear relationship with floral morphology. When surrounded by selfers, plants from the outcrosser population self-fertilize at nearly the same rate as selfers (>80%), but have much lower self male fitness due to reduced fruit set. Because outcross siring success is also extremely low (<8%) in this treatment, these mate-limited outcrossers are at male fitness disadvantage to both pseudocleistogamous selfers and nonlimited outcrossers. The relative male fitness of plants with different mating systems appears dependent on the ecological context, as well as on morphological trade-offs.

Biological Evolution↗
PubMed2001

Mimicry on the QT(L): genetics of speciation in Mimulus.

Ecological studies suggest that hummingbird-pollinated plants in North America mimic each other to increase visitation by birds. Published quantitative trait locus (QTL) data for two Mimulus species indicate that floral traits associated with hummingbird versus bee pollination results from a few loci with major effects on morphology, as predicted by classical models for the evolution of mimicry. Thus, the architecture of genetic divergence associated with speciation may depend on the ecological context.

Animals↗
PubMed2001

Sex among the flowers: the distribution of plant mating systems.

Previous reviews of plant outcrossing rate survey data have agreed that predominant selfing and predominant outcrossing are alternative stable states of mating system evolution. We reanalyzed the most recent data and plot outcrossing rates as a continuous variable rather than as a class variable. Wind-pollinated species are indeed bimodal. However, the shape of the distributions for animal-pollinated species reveals that intermediate rates of outcrossing are common (49% of species fall between 20% and 80% outcrossing). Consequently, we suggest that mating system is best considered a continuous rather than a discrete character of plant populations.

Adaptation, Physiological↗
PubMed2002

Age at maturity and diversification in woody angiosperms.

Angiosperm diversification has been associated with plant-animal interactions such as seed dispersal and pollination and life-history characters such as rapid growth and fast reproduction. This paper relates a life-history character (age at maturity) to woody angiosperm diversification. Here I present a comparative analysis of data drawn from the literature, indicating that time to first reproduction is shorter in woody angiosperms than in gymnosperms. In addition, age at maturity is negatively correlated with the rate of diversification (measured as the number of species per genus) at all the taxonomic levels analyzed and also when phylogenetically independent contrasts were conducted. This correlation suggests that early reproduction promotes diversification in woody angiosperms. Furthermore, this correlation is not a confounding effect of the association between age at maturity and other ecological factors that promote angiosperm diversification, such as pollination and seed dispersal systems.

Biological Evolution↗
PubMed2004

Expression of rolB in tobacco flowers affects the coordinated processes of anther dehiscence and style elongation.

The effect of auxin on stamen and pistil development in tobacco flowers was investigated by means of the localized expression of rolB (root loci B), an Agrobacterium oncogene that increases auxin sensitivity in a cell-autonomous fashion. When rolB is driven by the promoter of the meiosis-specific Arabidopsis gene DMC1 (disrupted meiotic cDNA 1), expression occurs earlier in male than in female developing organs, resulting in a delay in anther dehiscence with respect to normal timing of pistil development. As a consequence of this developmental uncoupling, self-pollination is prevented in pDMC1:rolB plants. Histological analysis of pDMC1:GFP plants indicates that in tobacco, this promoter is active not only in meiocytes but also in somatic tissues of the anther. In contrast, simultaneous expression of rolB in anther and pistil somatic tissues, achieved by expressing a construct containing rolB under the control of the promoter of the petunia gene FBP7 (floral binding protein 7), results in a concomitant delay of both anther dehiscence and pistil development without affecting self-pollination of the plants. Analysis of plants harboring the pFBP7:GUS construct shows that in tobacco, this promoter is active not only in the ovules, as described for petunia, but also in pistil and anther somatic tissues involved in the dehiscence program. The delay in anther dehiscence and pistil development could be phenocopied by exogenous application of auxin. Jasmonic acid (JA) could not rescue the delay in anther dehiscence. These results suggest that auxin plays a key role in the timing of anther dehiscence, the dehiscence program is controlled by the somatic tissues of the anther, and auxin also regulates pistil development.

Arabidopsis Proteins↗
PubMed1975

Ragweed hay fever: treatment by local passive administration of IgG antibody.

To determine whether the local administration of IgG antibodies might reduce the symptoms of ragweed hay fever, we tested the effect of this treatment in fourteen patients in a double-blind pilot trial. The patients were randomly divided into two groups, treatment and placebo, and their symptoms and medication usage were determined during the ragweed pollination season. One group used a nasal spray consisting of phosphate-buffered saline (PBS) containing human serum albumin, whereas the other used PBS containing purified IgG from a subject with a high titre of IgG antibody to partially purified ragweed antigen E. Treated and control groups used comparable quantities of nasal spray, and neither noted any ill effects. Comparison of individual symptoms of hay fever, medication usage, and total symptom scores showed no significant differences between the groups except a lessening of eye symptoms (P less than 0.05) in the treated group. The results suggest that nasal administration of IgG antibody up to five times daily does not alter the severity of symptoms in ragweed hay fever. Furthermore, total serum IgE protein and specific IgE levels increased comparably in both groups, suggesting that passive administration of IgG antibody does not suppress the production of IgE antibody during the pollination season.

Administration, Intranasal↗
PubMed1976

Qualitative and quantitative comparison of pollen calendars for plain and mountain areas.

A comparison of the quantity and the quality of pollen content in the atmosphere of two regions, one of the plains bordering the Mediterranean sea (altitude 40 m), the other of the mountains of the Pyrenees (altitude 1550 m), was made during the climatological year 1974-1975. The method which was used intercepts the pollen flux of the atmosphere with a vertical filtering unit, which is exposed facing the direction of wind on the filtering door of the weather-vane and collects much larger quantities of pollen than the other techniques of collection. The atmospheric currents displace from one region to another numerous spores and pollens, the trajectories of which are directly influenced by the general circulation of the atmosphere. The density of these fluxes can be very large, reaching 2500 grains/m3 of air at M.T.P.R. in the last week of January; the taxons collected are very numerous (more than 700). The atmospheric transfer of pollen modifies largely the pollen content of the atmosphere of different flowering domains. These interferences manifest themselves in the simplest cases by the presence of two peaks of concentration, the principal corresponding to the local efflorescence, the second to the pollen transferred from other regions. The pollen concentrations in the mountains are one-third of those in the plains. Pollination in the mountains is several weeks late in comparison to the plain during the first semester, whereas during the second semester, it is the plains that show a certain delay. These findings show why some allergic patients who go to the mountains during summer are affected twice by pollination.

Air Pollution↗
PubMed1983

A study on airborne allergenic pollen content of the atmosphere of Naples.

In this paper we describe the results of volumetric sampling of the airborne allergenic pollen content of the Naples atmosphere. These studies have been carried out continuously since 1 May 1979 until 31 December 1981 utilizing a Burkard volumetric spore trap. We found that the most important allergenic pollen in Naples air is Parietaria, with a very long-lasting period of pollination occurring from March to November. After Parietaria, Gramineae play an allergenic role frequently in association with the pollen of Olea, which is the most important pollen of all the trees in this area. In the summer/autumn seasons we observed in this area the pollination of mugwort (the unique plant of the Compositae) which was found to be of allergenic importance in Naples.

Adult↗