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PubMed1998

Differential expression of a novel gene in response to coronatine, methyl jasmonate, and wounding in the Coi1 mutant of Arabidopsis.

Coronatine is a phytotoxin produced by some plant-pathogenic bacteria. It has been shown that coronatine mimics the action of methyl jasmonate (MeJA) in plants. MeJA is a plant-signaling molecule involved in stress responses such as wounding and pathogen attack. In Arabidopsis thaliana, MeJA is essential for pollen grain development. The coi1 (for coronatine-insensitive) mutant of Arabidopsis, which is insensitive to coronatine and MeJA, produces sterile male flowers and shows an altered response to wounding. When the differential display technique was used, a message that was rapidly induced by coronatine in wild-type plants but not in coi1 was identified and the corresponding cDNA was cloned. The coronatine-induced gene ATHCOR1 (for A. thaliana coronatine-induced) is expressed in seedlings, mature leaves, flowers, and siliques but was not detected in roots. The expression of this gene was dramatically reduced in coi1 plants, indicating that COI1 affects its expression. ATHCOR1 was rapidly induced by MeJA and wounding in wild-type plants. The sequence of ATHCOR1 shows no strong homology to known proteins. However, the predicted polypeptide contains a conserved amino acid sequence present in several bacterial, animal, and plant hydrolases and includes a potential ATP/GTP-binding-site motif (P-loop).

Acetates↗
PubMed2003

The MSP1 gene is necessary to restrict the number of cells entering into male and female sporogenesis and to initiate anther wall formation in rice.

The function of the novel gene MSP1 (MULTIPLE SPOROCYTE), which controls early sporogenic development, was elucidated by characterizing a retrotransposon-tagged mutation of rice. The MSP1 gene encoded a Leu-rich repeat receptor-like protein kinase. The msp1 mutation gave rise to an excessive number of both male and female sporocytes. In addition, the formation of anther wall layers was disordered and the tapetum layer was lost completely. Although the mutation never affected homologous chromosome pairing and chiasma maintenance, the development of pollen mother cells was arrested at various stages of meiotic prophase I, which resulted in complete male sterility. Meanwhile, plural megaspore mother cells in a mutant ovule generated several megaspores, underwent gametogenesis, and produced germinable seeds when fertilized with wild-type pollen despite disorganized female gametophytes. In situ expression of MSP1 was detected in surrounding cells of male and female sporocytes and some flower tissues, but never in the sporocytes themselves. These results suggest that the MSP1 product plays crucial roles in restricting the number of cells entering into male and female sporogenesis and in initiating anther wall formation in rice.

Amino Acid Sequence↗
PubMed2004

48,000 years of climate and forest change in a biodiversity hot spot.

A continuous 48,000-year-long paleoecological record from Neotropical lower montane forest reveals a consistent forest presence and an ice-age cooling of approximately 5 degrees to 9 degrees C. After 30,000 years of compositional stability, a steady turnover of species marks the 8000-year-long transition from ice-age to Holocene conditions. Although the changes were directional, the rates of community change were no different during this transitional period than in the preceding 30,000-year period of community stability. The warming rate of about 1 degrees C per millennium during the Pleistocene-Holocene transition was an order of magnitude less than the projected changes for the 21st century.

Biodiversity↗
PubMed2002

Receptor kinase signaling in plant development.

The Arabidopsis genome sequence has revealed that plants contain a much larger complement of receptor kinase genes than other organisms. Early analysis of these genes revealed involvement in a diverse array of developmental and defense functions that included gametophyte development, pollen-pistil interactions, shoot apical meristem equilibrium, hormone perception, and cell morphogenesis. Amino acid sequence motifs and binding studies indicate that the ectodomains are capable of binding, either directly or indirectly, various classes of molecules including proteins, carbohydrates, and steroids. Genetic and biochemical approaches have begun to identify other components of several signal transduction pathways. Some receptor-like kinases (RLKs) appear to function with coreceptors lacking kinase domains, and genome analysis suggests this might be true for many RLKs. The KAPP protein phosphatase functions as a negative regulator of at least two RLK systems, and in vitro studies suggest it could be a common component of more. Whether plant signaling systems display a modularity similar to animal systems remains to be determined. Future efforts will reveal unknown functions of other RLKs and elucidate the relationships among their signaling networks.

Cell Differentiation↗
PubMed2002

[Temporal and geographic development of the main allergenic pollens in France: 1987-2001].

At various occasions, we presented the temporal and geographical evolution of pollination during ten to fifteen last years on various sites of the French network. The year 2000 had shown often different characteristics for some tax for part of the towns of France. An hypothesis had been suggested blaming the great storm at the end of December 1999. Work presented has pure goal to prolong of one year (2001) the curves of evolution of all taxa and those of main allergenic pollens so, the share to consolidate or not the assumption 2000 and the another share, to present the assessment of pollination during the season 2001.

Biological Evolution↗
PubMed2005

Clinical effects of specific immunotherapy: a two-year double-blind, placebo-controlled study with a one year follow-up.

BACKGROUND: A new depot allergoid of house dust mite (Dermatophagoides pteronyssinus - D.pt) has been created in line with the principles and methodology established in the successful development of pollen allergoids. A two-year double-blind placebo-controlled clinical trial, with one further follow-up year of active treatment, has been conducted to assess clinical efficacy and tolerance. METHODS: 40 patients (20 verum and 20 placebo) with IgE-mediated mite allergy and a history of moderate to severe perennial symptoms of rhinoconjunctivitis with or without asthma participated in a 2-year randomized, double-blind, placebo-controlled trial. Actively treated patients were included in a follow-up year. Active treatment was performed with an aluminium hydroxide adsorbed house dust mite allergoid. Parameters for baseline data and clinical efficacy: nasal challenge, quantitative skin prick testing, Visual Analog Scale (VAS), patients' diaries, physician's assessment of patients? health condition, symptoms and use of anti-allergic medication as well as adverse reactions and changes in specific IgG4 and IgE antibodies. RESULTS: The trial detected superiority (p < 0.05) of mite depot allergoid versus placebo with regard to VAS and symptom intensity sum score in patients who needed anti-allergic medication in the baseline period. Significant differences (p < 0.05) between verum and placebo groups were also seen for patients' reactivities to nasal challenges and prick tests with allergen. The blinded assessment by the physician documented a significant difference (p < 0.05) between the groups in favour of active treatment. After reaching the maximum dose as well as after 12 and 24 months, specific IgG4 antibody concentrations were significantly elevated in the verum group (p < 0.05) by comparison with placebo. Local reactions were less frequent in the verum group and no systemic adverse reactions occurred. A third year of active treatment resulted in further improvement and documented the advantage of booster therapy to stabilize the clinical success. CONCLUSION: Specific immunotherapy with a mite depot allergoid induced significant clinical improvements versus placebo. Safety was assessed as excellent, and no systemic adverse reactions occurred.

Adolescent↗
PubMed2006

The late pollen actins are essential for normal male and female development in Arabidopsis.

In angiosperms the late pollen actins (LPAs) are strongly expressed in mature pollen and pollen tubes and at much lower levels in ovules. Four Arabidopsis lines with homozygous knockout mutations in the four individual LPA genes displayed normal flowers, pollen, and seed set. However, when all four LPAs were silenced simultaneously with a single RNA interference (RNAi) construct targeting the 3'UTR of each mRNA, obvious reproductive defects were observed. Western analysis of various Late Pollen actin RNA interference (LPRi) epialleles showed total LPA protein and RNA expression levels were knocked down from 0% to 95% compared to wild-type levels. Reciprocal crosses with the RNAi lines demonstrated that lowered LPA expression was associated with defects in both male and female fertility. Strong epialleles showed significant reductions in normal silique and seed production and were nearly sterile. Dissection of the siliques from moderate LPRi epialleles revealed many unfertilized ovules, increased numbers of aborted seeds, and decreased numbers of healthy seeds. Microscopic analysis of LPRi pollen indicated that the pollen shape and size were normal, but pollen germinated poorly. While multiple LPA genes may have some functional redundancy, the combined expression of multiple LPA genes appears essential to normal male and female reproductive development.

Actins↗
PubMed2005

The reduction of rhinitis symptoms by nasal filters during natural exposure to ragweed and grass pollen.

BACKGROUND: Prototype nasal filters were developed to collect inhaled pollen. This study evaluated the efficacy of the filters for prevention of rhinitis symptoms during acute outdoor pollen exposure. METHODS: A randomized double-blind design was used. Subjects (n=46) with a history of autumn exacerbation of rhinitis and positive skin test to ragweed, Bermuda and/or Bahia grass wore either active or placebo nasal filters for 2 h in autumn in a park containing these species. Major and Total Symptoms scores were recorded at 0, 30, 60, 90 and 120 min. RESULTS: Subjects wearing active nasal filters had significantly reduced scores, at all time-points compared with placebo group (all P <0.05). Of 14 individual symptoms measured, seven were significantly reduced (number of sneezes, runny nose, itchy nose, sniffles, itchy throat; itchy eyes and watery eyes) and another three showed a trend towards lower severity. The nasal filters also enabled the resolution of existing symptoms. Maximal difference in symptoms was seen immediately after subjects had spent 20 min sitting beside a large patch of ragweed. CONCLUSION: This is the first clinical trial of a nasal filter. The results suggest it has potential for enhancing rhinitis management during acute allergen exposure.

Adolescent↗
PubMed2002

Male gametophyte development in bread wheat (Triticum aestivum L.): molecular, cellular, and biochemical analyses of a sporophytic contribution to pollen wall ontogeny.

Bread wheat (hexaploid AABBDD genome; 16 billion basepairs) is a genetically complex, self-pollinating plant with bisexual flowers that produce short-lived pollen. Very little is known about the molecular biology of its gametophyte development despite a longstanding interest in hybrid seeds. We present here a comprehensive characterization of three apparently homeologous genes (TAA1a, TAA1b and TAA1c) and demonstrate their anther-specific biochemical function. These eight-exon genes, found at only one copy per haploid complement in this large genome, express specifically within the sporophytic tapetum cells. The presence of TAA1 mRNA and protein was evident only at specific stages of pollen development as the microspore wall thickened during the progression of free microspores into vacuolated-microspores. This temporal regulation matched the assembly of wall-impregnated sporopollenin, a phenylpropanoid-lipid polymer containing very long chain fatty alcohols (VLCFAlc), described in the literature. Our results establish that sporophytic genes contribute to the production of fatty alcohols: Transgenic expression of TAA1 afforded production of long/VLCFAlc in tobacco seeds (18 : 1; 20 : 1; 22 : 1; 24 : 0; 26 : 0) and in Escherichia coli (14 : 0; 16 : 0; 18 : 1), suggesting biochemical versatility of TAA1 with respect to cellular milieu and substrate spectrum. Pollen walls additionally contain fatty alcohols in the form of wax esters and other lipids, and some of these lipids are known to play a role in the highly specific sexual interactions at the pollen-pistil interface. This study provides a handle to study these and to manipulate pollen traits, and, furthermore, to understand the molecular biology of fatty alcohol metabolism in general.

Amino Acid Sequence↗
PubMed2001

[Ultrastructural localization of ATPase activity in fertile and sterile anther of rice (Oryza sativa L. cv. Marxie)].

Pb3 (po4)2-precipitation was used to study the ATPase activities both in fertile and sterile anthers of rice (Oryza sativa L. cv. Marxie). At big-vacuole pollen stage, tapetum of the fertile anthers showed high ATPase activity in their nuclei. In fertile pollen, ATPase was localized on the outside surface of the exine and in the nucleus both at big-vacuole and at bi-nucleate pollen stage. At late bi-nucleate pollen stage, a large amount of Pb3 (PO4)2 precipitated in endintine of the fertile pollen. In sterile anthers, tapetum was fully degenerated at big-vacuole pollen stage. In sterile pollen, ATPase was localized both on the plasmamembrane and in intine. These phenomena lasted to the bi-nucleate pollen stage. In addition, most of the sterile pollen did not show well-developed endintine. Based on the above results, we suggested that abortive tapetum could not provide enough nutrition for pollen development, and the high ATPase activity both on plasma membrane and in intine would likely result in ATP shortage in sterile anthers.

Adenosine Triphosphatases↗
PubMed1998

Behavioral and electrophysiological dose-response relationships in adult western corn rootworm (Diabrotica virgifera virgifera LeConte) for host pollen amino acids.

A strong correlation is shown between taste cell inputs and phagostimulatory outputs with predominant dietary pollen amino acids for western corn rootworm, Diabrotica virgifera virgifera. Behavioral and electrophysiological dose-response profiles in adult beetles are presented for five major free amino acids in host pollens. Differential responses were found with strongest phagostimulation and sensory response elicited by L-alanine and L-serine, followed in order by L-proline and beta-alanine. gamma-Aminobutyric acid gave the weakest and most sporadic response. ED(50) values for phagostimulation and chemosensory input were 28.3nmol/disk and 13mM, respectively, for L-alanine and 17nmol/disk and 11mM, respectively, for serine. Threshold values for the responses were approximately 1-2mM. These behavioral and chemosensory dose-response ranges correspond closely to levels of free amino acids present in host plant pollens. Use of these response values in development of a pollen chemosensory code for western corn rootworm feeding is discussed.

Journal Article↗
PubMed2006

Arabidopsis HAP2 (GCS1) is a sperm-specific gene required for pollen tube guidance and fertilization.

In flowering plants, sperm cells develop in the pollen cytoplasm and are transported through floral tissues to an ovule by a pollen tube, a highly polarized cellular extension. After targeting an ovule, the pollen tube bursts, releasing two sperm that fertilize an egg and a central cell. Here, we identified the gene encoding Arabidopsis HAP2, demonstrating that it is allelic to GCS1. HAP2 is expressed only in the haploid sperm and is required for efficient pollen tube guidance to ovules. We identified an insertion (hap2-1) that disrupts the C-terminal portion of the protein and tags mutant pollen grains with the beta-glucuronidase reporter. By monitoring reporter expression, we showed that hap2-1 does not diminish pollen tube length in vitro or in the pistil, but it reduces ovule targeting by twofold. In addition, we show that the hap2 sperm that are delivered to ovules fail to initiate fertilization. HAP2 is predicted to encode a protein with an N-terminal secretion signal, a single transmembrane domain and a C-terminal histidine-rich domain. These results point to a dual role for HAP2, functioning in both pollen tube guidance and in fertilization. Moreover, our findings suggest that sperm, long considered to be passive cargo, are involved in directing the pollen tube to its target.

Amino Acid Sequence↗
PubMed1987

A method for staining pollen tubes in pistil.

A quadruple staining procedure has been developed for staining pollen tubes in pistil. The staining mixture is made by adding the following in the order given: lactic acid, 80 ml; 1% aqueous malachite green, 4 ml; 1% aqueous acid fuchsin, 6 ml; 1% aqueous aniline blue, 4 ml; 1% orange G in 50% alcohol, 2 ml; and chloral hydrate, 5 g. Pistils are fixed for 6 hr in modified Carnoy's fluid (absolute alcohol:chloroform:glacial acetic acid 6:4:1), hydrated in descending alcohols, transferred to stain and held there for 24 hr at 45 +/- 2 C. They were then transferred to a clearing and softening fluid containing 78 ml lactic acid, 10 g phenol, 10 g chloral hydrate and 2 ml 1% orange G. The pistils were held there for 24 hr at 45 +/- 2 C, hydrolyzed in the clearing and softening fluid at 58 +/- 1 C for 30 min, then stored in lactic acid for later use or immediately mounted in a drop of medium containing equal parts of lactic acid and glycerol for examination. Pollen tubes are stained dark blue to bluish red and stylar tissue light green to light greenish blue. This stain permits pollen tubes to be traced even up to their entry into the micropyle.

Fruit↗
PubMed2005

Elevated temperature during reproductive development affects cone traits and progeny performance in Picea glauca x engelmannii complex.

Two temperature regimes were applied during reproductive development of seed and pollen cones of interior spruce (Picea glauca (Moench) Voss and Picea engelmannii (Parry) complex) to determine temperature effects on the adaptive traits of progeny. In Experiment 1, identical crosses were made on potted interior spruce using untreated pollen followed by exposure to a day/night temperature of 22/8 or 14/8 degrees C with a 12-h photoperiod during the stages of reproductive development from post-pollination to early embryo development. Frost hardiness and growth of progeny from seed produced in the two temperature treatments were measured over a 4-year period. Elevated temperature significantly affected both seed-cone development and the adaptive properties of the progeny. Seed cones exposed to the 22/8 degrees C treatment reached the early embryo stage in 53 days versus 92 days in the 14/8 degrees C treatment. Seed yields, cotyledon emergence and percent germination were also significantly enhanced by the 22/8 degrees C treatment. Progeny from seed produced in the higher temperature treatment showed significantly reduced spring and fall frost hardiness, but the elevated temperature treatment had no significant effects on time of bud burst, growth patterns or final heights. In Experiment 2, single ramets of the same clone were subjected to a day/night temperature of 20/8 or 10/8 degrees C during pollen cone development, starting from meiosis and ending at pollen shedding. The two populations of pollen were then crossed with untreated seed cones. Compared with pollen cones exposed to the 10/8 degrees C treatment, pollen cones exposed to the 20/8 degrees C treatment during development reached the shedding stage 2-4 weeks earlier, whereas pollen yields, in vitro viability and fertility (seed set) were significantly lower; however, the resulting progeny displayed no treatment differences in frost hardiness or growth after 1 year. Results suggest that seed orchard after-effects could be caused by temperature differences between orchard site and parent tree origin and that this effect acts on maternal development. Gametophytic (pollen or megagametophyte or both) and early embryo (sporophytic) selection are possible mechanisms that may explain the observed results. Although the effects are biologically significant, they are relatively small and do not justify changes in current deployment strategies for seed orchard seed.

Hot Temperature↗
PubMed1994

Characterization of four new beta-tubulin genes and their expression during male flower development in maize (Zea mays L.).

Four different beta-tubulin coding sequences were isolated from a cDNA library prepared from RNA from maize seedling shoots. The four genes (designated tub4, tub6, tub7 and tub8) represented by these cDNA clones together with the tub1 and tub2 genes reported previously encode six beta-tubulin isotypes with 90-97.5% amino acid sequence identity. Results from phylogenetic analysis of 17 beta-tubulin genes from monocot and dicot plant species indicated that multiple extant lines of beta-tubulin genes diverged from a single precursor after the appearance of the two major subfamilies of alpha-tubulin genes described previously. Hybridization probes from the 3' non-coding regions of six beta-tubulin clones were used to quantify the levels of corresponding tubulin transcripts in different maize tissues including developing anthers and pollen. The results from these dot blot hybridization experiments showed that all of the beta-tubulin genes were expressed in most tissues examined, although each gene showed a unique pattern of differential transcript accumulation. The tub1 gene showed a high level of transcript accumulation in meristematic tissues and almost no accumulation in the late stages of anther development and in pollen. In contrast, the level of tub4 transcripts was very low during early stages of male flower development but increased markedly (more than 100 times) during the development of anthers and in pollen. Results from RNAse protection assays showed that this increased hybridization signal resulted from expression of transcripts from one or two genes closely related to tub4. The tub4-related transcripts were not present in shoot tissue. Transcripts from the tub2 gene accumulated to very low levels in all tissues examined, but reached the highest levels in young anthers containing microspore mother cells. RNAse protection assays were used to measure the absolute levels of alpha- and beta-tubulin transcripts in seedling shoot and in pollen. The alpha-tubulin gene subfamily I genes (tua1, tua2, tua4) contributed the great majority of alpha-tubulin transcripts in both shoot and pollen. Transcripts from the beta-tubulin genes tub4, tub6, tub7, and tub8 were predominant in shoot, but were much less significant than the tub4-related transcripts in pollen.

Amino Acid Sequence↗
PubMed2002

[Investigation of the pollen chromatin state of Hippeastrum hibridum at the early stages of development with fluorescent dye Hoechst 33342].

The work was carried out on the pollen of Hippeastrum hibridum, whose size (ca 55 mcm) permits to follow both the pollen tube formation and development of the vegetative nucleus and generative cell within the first two hours before the growing point arising. Using fluorescent dye Hoechst 33342 chromatin state alterations accompanying changes in the pollen physiological state were investigated. The maximum fluorescent intensity was observed in 30 min of staining and reflected the maximum chromatin functional activity. Histograms of pollen distribution according to fluorescent intensity differ considerably with doses of irradiation (500, 1000, 2000, 3000 and 4000 Gy). Besides, a germinative index of fluorescence intensity was calculated. A comparative analysis of these data has shown that the lowest decrease in fluorescent intensity observed at 500, 3000 and 4000 Gy, was accompanied by different germinative indices. At 500 Gy, the index was 2.5 times lower than in the control, but at 4000 G no germination was not noted. The process of pollen grain development is supposed to be more intensive and faster at 500 Gy, than in the control. At 4000 Gy, a decrease in the functional pollen activity is accompanied by decrease or inhibition of chromatin functional activity.

Benzimidazoles↗