Abstract Detail

Seed plant gametophytes: Still the forgotten generation?!?

Dickinson, Hugh G. [1], Keith-Lucas, Alanna [1], Bourdon, Valerie [1].

Why do gametophytes need so many cytokinetic mechanisms?.

Angiosperm gametophytes are cytokinetic chimaeras. The microspores giving rise to pollen grains are derived from nuclear-cytoplasmic domains (NCDs) established at the end of meiosis by a radial microtubule system (RMS) (Brown and Lemmon 2001). By contrast, pollen mitosis I appears to be a ‘classical’, if asymmetric, plant cytokinesis, and the cytoskeleton associated with pollen mitosis II remains poorly characterised. The female gametophyte is derived from a RMS-type division, and the first divisions of the surviving megaspore involve a cytokinetic apparatus which – while not identical – contains features of the ‘meiotic’ RMS system. Strikingly, following double fertilisation (fusion of one sperm with the diploid central cell, and the other with the egg) the two structures formed follow very different cytokinetic pathways, the endosperm developing coenocytically via an RMS system, the egg undergoing classical plant cytokinesis from its very first division. The identification of genes required specifically for the RMS-type of cytokinesis - such as TETRASPORE which encodes a kinesin (Yang et al 2003) - now opens the way for functional analysis of the RMS itself, and also comparison between the different forms of cytokinesis occurring in gametophytes. Data from this work, combined with the study of cell types undergoing the different forms of cytokinesis, and their lineages, are pointing to clear functional differences between these mechanisms of cell division. They are also beginning to provide clues as to why evolution has selected such a wide range of cytokinetic systems in a generation which, in temporal terms at least, represents such a short phase of the angiosperm life history. Brown, R. and Lemmon, B. 2001 Protoplasma 215: 35-49. Yang, C-Y et al 2003 Plant Journal 34:229-240

1 - University of Oxford, Department of Plant Sciences, South Parks Rd., Oxford, OX1 3RB, United Kingdom

Keywords:
Cytokinesis
cytoskeleton
embryo sac
gametogenesis
polarity
pollen
radial microtubular system
TETRASPORE.

Presentation Type: Symposium
Session: 6-3
Location: Ballroom 1 (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 9:00 AM
Abstract ID:900