Timing is everything: highly specific and transient expression of a MAP kinase determines auxin-induced leaf venation patterns in Arabidopsis.

Mitogen-activated protein kinase (MAPK) cascades are universal signal transduction modules present in all eukaryotes. In plants, MAPK cascades were shown to regulate cell division, developmental processes, stress responses, and hormone pathways. The subgroup A of Arabidopsis MAPKs consists of AtMPK3, AtMPK6, and AtMPK10.

A tobacco homolog of DCN1 is involved in pollen development and embryogenesis.

We show that DCN1 binds ubiquitin and RUB/NEDD8, associates with cullin, and is functionally conserved. DCN1 activity is required for pollen development transitions and embryogenesis, and for pollen tube growth. Plant proteomes show remarkable plasticity in reaction to environmental challenges and during developmental transitions.

The endoplasmic reticulum localized PIN8 is a pollen-specific auxin carrier involved in intracellular auxin homeostasis.

The plant hormone auxin is a mobile signal which affects nuclear transcription by regulating the stability of auxin/indole-3-acetic acid (IAA) repressor proteins. Auxin is transported polarly from cell to cell by auxin efflux proteins of the PIN family, but it is not as yet clear how auxin levels are regulated within cells and how access of auxin to the nucleus may be controlled. The Arabidopsis genome contains eight PINs, encoding proteins with a similar membrane topology.

Detection of antigens reactive to IgE and IgA during wheat seed maturation and in different wheat cultivars.

Background: Dietary intake of wheat causes hypersensitivity reactions in patients suffering from IgE-mediated food allergy and coeliac disease.

Aim: To study the expression of IgE- and IgA-reactive antigens during wheat seed maturation and in different wheat cultivars.

Methods: Summer wheat was grown in a glasshouse and seeds were harvested at defined maturation stages.

Molecular and immunological characterization of a wheat serine proteinase inhibitor as a novel allergen in baker's asthma.

IgE-mediated sensitization to wheat flour belongs to the most frequent causes of occupational asthma. A cDNA library from wheat seeds was constructed and screened with serum IgE from baker's asthma patients. One IgE-reactive phage clone contained a full-length cDNA coding for an allergen with a molecular mass of 9.

The resurgence of haploids in higher plants.

The life cycle of plants proceeds via alternating generations of sporophytes and gametophytes. The dominant and most obvious life form of higher plants is the free-living sporophyte. The sporophyte is the product of fertilization of male and female gametes and contains a set of chromosomes from each parent; its genomic constitution is 2n.

Combination of reversible male sterility and doubled haploid production by targeted inactivation of cytoplasmic glutamine synthetase in developing anthers and pollen.

Reversible male sterility and doubled haploid plant production are two valuable technologies in F(1)-hybrid breeding. F(1)-hybrids combine uniformity with high yield and improved agronomic traits, and provide self-acting intellectual property protection. We have developed an F(1)-hybrid seed technology based on the metabolic engineering of glutamine in developing tobacco anthers and pollen.

In situ molecular identification of the Ntf4 MAPK expression sites in maturing and germinating pollen.

Background Information: MAPKs (mitogen-activated protein kinases) are involved in the transduction of different signals in eukaryotes. They regulate different processes, such as differentiation, proliferation and stress response. MAPKs act through the phosphorylation cascade, being the last element that phosphorylates the final effector of the cell response.

Two tobacco proline dehydrogenases are differentially regulated and play a role in early plant development.

Proline dehydrogenase is the rate-limiting enzyme in proline degradation and serves important functions in the stress responses and development of plants. We isolated two tobacco proline dehydrogenases, NtPDH1 and NtPDH2, in the course of screening for genes upregulated in stressed tobacco (Nicotiana tabacum) microspores. Expression analysis revealed that the two genes are differentially regulated.

Transcriptional and metabolic profiles of stress-induced, embryogenic tobacco microspores.

Higher plant microspores, when subjected to various stress treatments in vitro, are able to reprogram their regular gametophytic development towards the sporophytic pathway to form haploid embryos and plants. Suppression subtractive hybridization (SSH) and metabolic profiling were used to characterize this developmental switch. Following differential reverse Northern hybridizations 90 distinct up-regulated sequences were identified in stressed, embryogenic microspores (accessible at www.

Efficient embryogenesis and regeneration in freshly isolated and cultured wheat (Triticum aestivum L.) microspores without stress pretreatment.

The major advantage of doubled haploids in plant breeding is the immediate achievement of complete homozygosity. Desired genotypes are thus fixed in one generation, reducing time and cost for cultivar or inbred development. Among the different technologies to produce doubled haploids, microspore embryogenesis is by far the most common.

Methotrexate is a new selectable marker for tobacco immature pollen transformation.

We report here a new selectable marker for tobacco immature pollen transformation based on the expression of dihydrofolate reductase (dhfr) gene which confers resistance to methotrexate (Mtx). Two immature pollen transformation approaches, i.e.

Identification of a villin-related tobacco protein as a novel cross-reactive plant allergen.

In a paradigmatic approach we identified cross-reactive plant allergens for allergy diagnosis and treatment by screening of a tobacco leaf complementary DNA (cDNA) library with serum IgE from a polysensitized allergic patient. Two IgE-reactive cDNA clones were isolated which code for proteins with significant sequence similarity to the actin-binding protein, villin. Northern- and Western-blotting demonstrate expression of the villin-related allergens in pollen and somatic plant tissues.

The Arabidopsis thaliana MEK AtMKK6 activates the MAP kinase AtMPK13.

Mitogen-activated protein (MAP) kinases mediate cellular responses to a wide variety of stimuli. Activation of a MAP kinase occurs after phosphorylation by an upstream dual-specificity protein kinase, known as a MAP kinase kinase or MEK. The Arabidopsis thaliana genome encodes 10 MEKs but few of these have been shown directly to activate any of the 20 Arabidopsis MAP kinases.

MAP kinase phosphorylation of plant profilin.

Profilin is a small actin-binding protein and is expressed at high levels in mature pollen where it is thought to regulate actin filament dynamics upon pollen germination and tube growth. The majority of identified plant profilins contain a MAP kinase phosphorylation motif, P-X-T-P, and a MAP kinase interaction motif (KIM). In in vitro kinase assays, the tobacco MAP kinases p45(Ntf4) and SIPK, when activated by the tobacco MAP kinase kinase NtMEK2, can phosphorylate the tobacco profilin NtProf2.

A model system to study the environment-dependent expression of the Bet v 1a gene encoding the major birch pollen allergen.

Background: The major birch pollen allergen Bet v 1 (or Bet v 1a) is one of the main causes of seasonal type I allergies. Various environmental factors such as light, temperature and air pollution may influence the activity of the Bet v 1a gene. The creation of a model system to evaluate the role of environmental factors affecting the Bet v 1a gene expression would be highly desirable.

The MAP kinase kinase NtMEK2 is involved in tobacco pollen germination.

The tobacco ntf4 mitogen-activated protein (MAP) kinase gene (and its encoded protein p45(Ntf4)) is expressed at later stages of pollen maturation. We have found that the highly related MAP kinase SIPK is also expressed in pollen and, like p45(Ntf4), is activated upon pollen hydration. The MAP kinase kinase NtMEK2 activates SIPK, and here we show that it can also activate p45(Ntf4).

Regulation of developmental pathways in cultured microspores of tobacco and snapdragon by medium pH.

The regulation of developmental pathways in cultured microspores of tobacco ( Nicotiana tabacum L) and snapdragon ( Antirrhinum majus L) by medium pH is described for the first time. Unicellular tobacco and snapdragon microspores developed into normal, fertile pollen when cultured in media T1 and AT3 at pH 7.0 and 25 degrees C for 6 and 8 days, respectively.

A plant cyclin B2 is degraded early in mitosis and its ectopic expression shortens G2-phase and alleviates the DNA-damage checkpoint.

Mitotic progression is timely regulated by the accumulation and degradation of A- and B-type cyclins. In plants, there are three classes of A-, and two classes of B-type cyclins, but their specific roles are not known. We have generated transgenic tobacco plants in which the ectopic expression of a plant cyclin B2 gene is under the control of a tetracycline-inducible promoter.

A topoisomerase II-dependent checkpoint in G2-phase plant cells can be bypassed by ectopic expression of mitotic cyclin B2.

DNA topoisomerase II is required for mitotic chromosome condensation and segregation. Here we characterize the effects of inhibiting DNA topoisomerase II activity in plant cells using the non-DNA damaging topoisomerase II inhibitor ICRF-193. We report that ICRF-193 abrogated chromosome condensation in cultured alfalfa (Medicago sativa L.

Antirrhinum majus microspore maturation and transient transformation in vitro.

The male gametophyte of higher plants represents an excellent system to study gene regulation, cell fate determination and cellular differentiation in plants because of its relative simplicity compared to the sporophyte and its accessibility for cytological and molecular analysis. Unicellular plant microspores are single haploid cells, which can be isolated in large amounts at a defined developmental stage. Microspores cultured in vitro in a rich medium develop into mature pollen grains, which are fertile upon pollination in vivo.