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Virginia Walbot – One of the best experts on this subject based on the ideXlab platform.

  • pre meiotic Anther development
    Current Topics in Developmental Biology, 2019
    Co-Authors: Karina Van Der Linde, Virginia Walbot


    Abstract Most genetic and molecular analyses of Anther development utilize Arabidopsis thaliana, Oryza sativa (rice), and Zea mays (maize). Especially in maize, early stages of Anther development are easy to study because: (1) Maize has unisex flowers. (2) Compared to rice or A. thaliana, maize Anthers are relatively large, making dissection for molecular and biochemical analyses easy. (3) Anther developmental stage is strongly correlated with maize Anther length. Besides these technical advantages, understanding Anther and pollen development in maize is of significant agricultural importance. Today maize is a worldwide cereal crop: approximately 25% of all consumed food contains maize. Yield stability or even increases depend on maintenance of hybrid vigor, and production of hybrid seed requires manual detasseling or genetic control of pollen development. Knowledge of pollen development can also be used to manage transgene containment. In the first section of this chapter, we will describe the current model for sequential cell fate specification in maize Anther lobes, with reference to rice and A. thaliana to point out similarities and differences. In the second section of this chapter, we will review what is known about the individual cell types in Anther lobes. The diversity of Anther organization is addressed to a limited extent by cytological studies of Anthers, often directed to clarify taxonomic relationships. In the third section, we will comment on how new lines of investigation could clarify questions remaining in our current appreciation of Anther development.

  • chloroplasts in Anther endothecium of zea mays poaceae
    American Journal of Botany, 2015
    Co-Authors: Katherine M Murphy, Rachel L Egger, Virginia Walbot


    PREMISE OF THE STUDY: Although Anthers of Zea mays, Oryza sativa, and Arabidopsis thaliana have been studied intensively using genetic and biochemical analyses in the past 20 years, few updates to Anther anatomical and ultrastructural descriptions have been reported. For example, no transmission electron microscopy (TEM) images of the premeiotic maize Anther have been published. Here we report the presence of chloroplasts in maize Anthers. METHODS: TEM imaging, electron acceptor photosynthesis assay, in planta photon detection, microarray analysis, and light and fluorescence microscopy were used to investigate the presence of chloroplasts in the maize Anther. KEY RESULTS: Most cells of the maize subepidermal endothecium have starch-containing chloroplasts that do not conduct measurable photosynthesis in vitro. CONCLUSIONS: The maize Anther contains chloroplasts in most subepidermal, endothecial cells. Although maize Anthers receive sufficient light to photosynthesize in vivo and the maize Anther transcribes >96% of photosynthesis-associated genes found in the maize leaf, no photosynthetic light reaction activity was detected in vitro. The endothecial cell layer should no longer be defined as a complete circle viewed transversely in Anther lobes, because chloroplasts are observed only in cells directly beneath the epidermis and not those adjacent to the connective tissue. We propose that chloroplasts be a defining characteristic of differentiated endothecial cells and that nonsubepidermal endothecial cells that lack chloroplasts be defined as a separate cell type, the interendothecium.

  • male reproductive development gene expression profiling of maize Anther and pollen ontogeny
    Genome Biology, 2008
    Co-Authors: David S Skibbe, John Fernandes, Virginia Walbot


    During flowering, central Anther cells switch from mitosis to meiosis, ultimately forming pollen containing haploid sperm. Four rings of surrounding somatic cells differentiate to support first meiosis and later pollen dispersal. Synchronous development of many Anthers per tassel and within each Anther facilitates dissection of carefully staged maize Anthers for transcriptome profiling. Global gene expression profiles of 7 stages representing 29 days of Anther development are analyzed using a 44 K oligonucleotide array querying approximately 80% of maize protein-coding genes. Mature haploid pollen containing just two cell types expresses 10,000 transcripts. Anthers contain 5 major cell types and express >24,000 transcript types: each Anther stage expresses approximately 10,000 constitutive and approximately 10,000 or more transcripts restricted to one or a few stages. The lowest complexity is present during meiosis. Large suites of stage-specific and co-expressed genes are identified through Gene Ontology and clustering analyses as functional classes for pre-meiotic, meiotic, and post-meiotic Anther development. MADS box and zinc finger transcription factors with constitutive and stage-limited expression are identified. We propose that the extensive gene expression of Anther cells and pollen represents the key test of maize genome fitness, permitting strong selection against deleterious alleles in diploid Anthers and haploid pollen. Because flowering plants show a substantial bias for male-sterile compared to female-sterile mutations, we propose that this fitness test is general. Because both somatic and germinal cells are transcriptionally quiescent during meiosis, we hypothesize that successful completion of meiosis is required to trigger maturation of Anther somatic cells.

B Buter – One of the best experts on this subject based on the ideXlab platform.

  • The improvement in regenerated doubled haploids from Anther culture of wheat by Anther transfer
    Plant Cell Tissue and Organ Culture, 2000
    Co-Authors: A. Redha, B Buter, S.m.s. Islam, P. Stamp, J E Schmid


    This study was conducted to determine the most suitable method of regeneration by comparing two approaches: transfer of Anthers (with and without embryo-like structures) to regeneration conditions after a period of two to four weeks on induction medium (= Anther-transfer treatment) and transfer of embryo-like structures to regeneration conditions after five to eight weeks on induction medium. The early transfer of Anthers brought about a significant reduction in the number of embryos formed, but nevertheless significantly improved the frequency of plant regeneration. Combining an optimal date of Anther transfer with the early addition of colchicine to the induction medium (100 mg l^−1 for 1 and 3 days) led to an increase in the number of doubled haploid regenerants. The results indicate that transferring the Anthers after 28 days and adding 100 mg l^−1 colchicine to the induction medium on one day only caused a significant improvement in the ability of green plants to regenerate (7.0 compared to 0.50) as well as in chromosome doubling (success index: 4.0 compared to 0.33).

  • colchicine mediated chromosome doubling during Anther culture of maize zea mays l
    Theoretical and Applied Genetics, 1996
    Co-Authors: S Saisingtong, J E Schmid, Peter Stamp, B Buter


    Efficient methods of chromosome doubling are critical for the production of microspore-derived, doubled-haploid (=DH) plants, especially if, as in maize Anther culture, spontaneous chromosome doubling occurs infrequently. In the present study, colchicine (5–1000 mg/l) was added to the induction medium and maize Anthers were incubated in the colchicine-containing medium for different durations (1–7 days). In order to improve overall Anther culture response, the culture temperature was adjusted to 14°C during the first 7 days. Colchicine applied at low concentration, i.e. 5 mg/l (7 days), or for short duration, i.e. 1–3 days (250 mg/l), showed beneficial effects on the formation of embryolike structures (=ES) and thus led to increased plant production, but was comparatively ineffective regarding chromosome doubling. Optimal doubling effects were observed when Anthers had been exposed to culture medium containing 250 and 1000 mg/l of colchicine (7 days); in these treatments the doubling index (=DI), defined as the quotient of the number of DH plants and the number of totally regenerated plants in a specific treatment, rose to 0.56 and 0.53, respectively, compared to 0.20 in the untreated control. However, colchicine administered at concentrations higher than 250 mg/l seemed to be detrimental to general plant production; thus, in spite of a high DI, the overall DH plant production was even lower than in the control treatment. Maximum DH plant production for three different genotypes was accomplished with culture medium containing 250 mg/l of colchicine (7 days). With the best-responding genotype (ETH-M 36) a DH plant production of 9.9 DH plants/100 Anthers was accomplished, i.e. a 7-fold increase compared to the non-treated Anthers. This is the first report on efficient chromosome doubling in Anther culture by subjecting Anthers to colchicinecontaining induction medium during a post-plating cold treatment. Chromosome doubling as described here becomes an integral part of the maize Anther culture protocol and thus represents a rapid and economical way to produce DH plants.

Gynheung An – One of the best experts on this subject based on the ideXlab platform.

  • wax deficient Anther1 is involved in cuticle and wax production in rice Anther walls and is required for pollen development
    The Plant Cell, 2006
    Co-Authors: Kihong Jung, Lukas Schreiber, Rochus Franke, Andrea Faust, Alexander Yephremov, Heinz Saedler, Inhwan Hwang, Gynheung An


    In vegetative leaf tissues, cuticles including cuticular waxes are important for protection against nonstomatal water loss and pathogen infection as well as for adaptations to environmental stress. However, their roles in the Anther wall are rarely studied. The innermost layer of the Anther wall (the tapetum) is essential for generating male gametes. Here, we report the characterization of a T-DNA insertional mutant in the Wax-deficient Anther1 (Wda1) gene of rice (Oryza sativa), which shows significant defects in the biosynthesis of very-long-chain fatty acids in both layers. This gene is strongly expressed in the epidermal cells of Anthers. Scanning electron microscopy analyses showed that epicuticular wax crystals were absent in the outer layer of the Anther and that microspore development was severely retarded and finally disrupted as a result of defective pollen exine formation in the mutant Anthers. These biochemical and developmental defects in tapetum found in wda1 mutants are earlier events than those in other male-sterile mutants, which showed defects of lipidic molecules in exine. Our findings provide new insights into the biochemical and developmental aspects of the role of waxes in microspore exine development in the tapetum as well as the role of epicuticular waxes in Anther expansion.