Seed plant gametophytes: Still the forgotten generation?!?
Grossniklaus, Ueli , Gross-Hardt, Rita , Huck, Norbert , Escobar, Juan-Miguel , Moore, James M. , Gheyselinck, Jacqueline .
Genetic dissection of female gametophyte development and double fertilization.
The plant life cycle alternates between a diploid and a haploid generation, the sporophyte and the gametophyte. In the ovule, a single cell gets committed to the reproductive pathway, undergoes meiosis, and forms a tetrad of megaspores. In most species, only one megapore survives and typically forms an eight-nucleated embryo sac through a series of mitotic divisions (Grossniklaus and Schneitz, 1998; Yang and Sundaresan 2000). The genetic control of embryo sac development and fertilization is still very poorly understood. In order to identify genes involved in female gametophyte development and function we performed an insertional mutagenesis screen using the transposon system developed by Sundaresan et al. (1995) on the basis of reduced fertility and segregation ratio distortion (Moore et al. 1997; Howden et al.1998). A large number of mutants affect gameotphyte development and the double fertilization process. One of our interests is in cell specification and we will present the characterization of three mutants involved in the specification of the egg cell. A second focus are cell-cell interactions during fertilization. We will report on the molecular characterization of feronia, a mutant that defines a novel signaling process between male and female gametophytes at fertilization. In feronia, the pollen tubes, even if wild-type, are unable to release the sperm cells into the synergids to effect fertilization. This phenotype suggests that the female gametophyte plays a crucial role in pollen tube reception and, thus, controls the behavior of the male gametophyte. In addition to these cell-cell interactions at the level of the gametophytes we also investigated interactions at the level of the gametes. Using maize as a model system, we show that the female gametes of plants do not have a fast block to prevent polyspermy, suggesting that the cellular interactions at the level of the gametes differ between animals and plants.
1 - University of Zürich, Institute of Plant Biology & Zürich-Basel Plant Science Center, Zollikerstrasse 107, Zürich, CH-8008, Switzerland
Presentation Type: Symposium
Location: Ballroom 1 (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 9:45 AM