In Recognition of the Forgotten Generation D. L. MULCAHyl Pollen was long believed to serve primarily a single function, that of delivering male gametes to the egge A secondary and generally overlooked value of pollen is that it serves to block the transmission of many defective alleles and gene combinations into the next generation. This latter function comes about simply because pollen tubes carrying defective haploid genotypes frequently fail to complete growth through the entire length of the style. However, the beneficial consequences of this pollen selection are diluted by the fact that the same deleterious genotypes are often transmitted through the egg at strictly mendelian frequencies (Khush, 1973). Gene expression in the pollen might thus at least appear to be a phenomenon of trivial consequence. Indeed, Heslop-Harrison (1979) rightly termed the gametophytic portion of the angiosperm life cycle, the "forgotten generation." This neglect, however, came about despite subtle but constant indications that pollen is the site of intense gene activity and selection. For example, Mok and Peloquin (1975) demonstrated that relatively heterozygous diploid pollen shows heterotic characteristics whereas relatively homozygous diploid pOllen does not. This was proof positive that genes are expressed (that is, transcribed and translated) in the pollen. 1 Department of Botany, University of Massachusetts Amherst, MA 01003, USA viii However, the implications for pollen biology of even this recent and well known study were not widely recognized.
Inhaltsverzeichnis
Gene Expression in Pollen.- Expression of ?-Galactosidase Gene in Pollen of Brassica campestris.- Identification of Duplicate Loci and Evidence for Post-meiotic Gene Expression in Pollen.- Gametophytic Gene Expression in Embryo-lethal Mutants of Arabidopsis thaliana.- Pollen Competitive Ability in Maize Selection and Single Gene Analysis.- Extent of Gene Expression at the Gametophytic Phase in Maize.- Male Gametophyte Response to High Temperature in Maize.- Genes and their Expression in the Male Gametophyte of Flowering Plants.- Pollen in Biotechnology.- Chromosome Engineering with Meiotic Mutants.- Intergeneric Crosses Between Zea and Pennisetum Reciprocally by In Vitro Methods.- Gametophyte Transformation in Maize (Zea mays, Gramineae).- Attempts to Transform for Kanamycin-Resistance in Mature Pollen of Tobacco.- Attempted Pollen-mediated Transformation using Ti-plasmids.- Dissolution of Pollen Intine and Release of Sporoplasts.- Sporophytic Screening and Gametophytic Verification of Phytotoxin Tolerance in Sugarbeet (Beta vulgaris L.).- Predicting Species Response to Ozone using a Pollen Screen.- In Vitro and in Vivo Effects of Acidity and Trace Elements on Pollen Function.- Alfalfa Pollen and Callus Responses to Fusarium.- Induction of Gametic Selection in situ by Stylar Application of Selective Agents.- Factors Influencing Artificial Gametophyte Selections using Synthetic Stigmas.- In Vitro Reaction Between Apple Pollen and Apple Scab Fungus (Venturia inaequalis Cke. Wint.).- Pollen Selection in Breeding Glasshouse Tomatoes for Low Energy Conditions.- Biochemical Alterations in the Sexual Partners Resulting from Environmental Conditions before Pollination Regulate Processes after Pollination.- The Use of In Vitro Methods in the Production of Pollen.- Maize Pollen Research: Preliminary Reports from Two Projects Investigating Gamete Selection.- Pollen Storage Effects on Early Seedling Growth in Maize.- Pollen Selection Through Storage: A Tool for Improving True Potato Seed Quality?.- (...)