Home page of CSIRO: Dr. Abed Chaudhury
The embryo sac of Arabidopsis is seven nucleate with a haploid egg flanked by two synergid haploid cells at the micropylar end, diploid central nucleus formed by the fusion of two polar nuclei, and three haploid polar cells called antipodals at the chalazal end.
Three genes in Arabidopsis : FIS 1 (MEA), FIS3 (FIE) (FIS = fertilization- independent endosperm; MEA= MEDEA ) involved in seed development, were earlier identified by Dr. Chaudhury of CSIRO, Australia, R. Fischer of UCB and Grossniklaus of CSH. In all the three mutants, fis1, fis3 and fie, the endosperm develops without pollination; and in contrast to their normal counterparts, the growth of the embryo in these mutants stops after pollination. Proc Natl Acad Sci U S A. 2000 Sep 12;97(19):10637-42.
These mutants share one characteristic, i.e., they die or their embryo shows abnormal development only when the female parent contributes to the mutant allele. In other words, the effect is maternal. In the September 2000 issue of PNAS, Abed Chaudhury and his associates have published the results of their recent findings on the role of the above genes in seed development with or without pollination. The CSIRO scientists fused the promoters of the above three genes within the GUS (β-glucuronidase) gene. They detected the presence of the FIS2GUS fusion product in each of the polar cell nuclei, and in the central cell nucleus with no traceable activity in the cenocytic multi-nucleate endosperm tissue. The activity pattern of MEAGUS was found to be similar to that of FIS2GUS and the fusion product was detectable in embryo sac both before and after pollination. Based on their observations that (1) all the mutants have similar phenotype, (2) their gene products are detectable in the same parts of the embryo sac and (3) that they interact in a yeast two-hybrid system, they concluded that all the three genes under review are involved in seed development and that their products act in a similar fashion.