Gametophytic Gene Expression
The male gametophyte of flowering plants is a microscopic structure which during its early development is enclosed within the sporophyte tissue in the anther of a flower bud. Dramatic advances have been made recently in our understanding of gene expression in the different tissues of the anther including the tapetum (Koltunow et al, 1990: Mariani et al, 1990). Following meiosis there is a long interphase period during which the microspores enlarge greatly in size. Microspore mitosis results in an unequal partitioning of cytoplasm into the vegetative and generative cells. Following anthesis the pollen grain is deposited on the stigma of the pistil where it begins another phase of its development by germinating and extruding a tube within which the sperm cells are transported to the embryo sac. In many species studied the pollen grain at maturity contains all the proteins that are required for germination and early tube growth, since protein synthesis inhibitors do not block these events. Moreover a large number of enzymes have been reported to be present in pollen grains of various species (Mascarenhas, 1975). Protein synthesis begins early in pollen germination. Most of the studies in the literature indicate that the mature pollen grain contains a store of stable mRNAs that are translated early during germination and that play a greater or lesser role in pollen germination and tube growth depending on the plant species (reviewed in Mascarenhas, 1975, 1990a,b).
KeywordsPollen Development Pollen Germination Male Gametophyte Kentucky Bluegrass Male Gametophyte Development
Unable to display preview. Download preview PDF.
- Hamilton DA, Bashe DM, Stinson JR, Mascarenhas JP. 1989. Characterization of a pollen-specific genomic clone from maize. Sex. Plant Reprod. 2, 208–212.Google Scholar
- Mohapatra S, Hill R, Astwood J, Ekramoddoulah AKM, Olson E, Silvanovich A, Hatton T, Kisil FT, Sehon A (1990) Isolation and characterization of a cDNA clone encoding an IgE-binding protein from Kentucky bluegrass (Poa pratensis) pollen. Int Arch Allergy Appl Immunol 91: 362–368Google Scholar
- Rafner T, Griffith IJ, Kuo MC, Bond JF, Rogers BL, Klapper DG (1991) Cloning of Amb aI (antigen E), the major allergen family of short ragweed pollen. J Biol Chem 206: 1229–1236Google Scholar
- Singh MB, Hough T, Theerakulpisut P, Avjioglu A, Davies S, Smith PM, Taylor P, Simpson RJ, Ward LD, McCluskey J, Puy R, Knox RB (1991) Isolation of cDNA encoding a newly identified major allergenic protein of rye-grass pollen: intracellular targetting to the amyloplast. Proc Natl Acad Sci USA 88: 1384–1388PubMedCrossRefGoogle Scholar
- Valenta R, Duchene M, Pettenburger K, Sillaber C, Valent P, bettelheim P, Breitenbach M, Rumpold H, Kraft D, Scheiner O (1991) Identification of profilin as a novel pollen allergen; IgE autoreactivity in sensitized individuals. Science 253: 557–560Google Scholar