Genes controlling fertilization-independent seed development in Arabidopsis thaliana

We have cloned two genes, FIS1 and FIS2, that control both fertilization in dependent seed development and postpollination embryo development in Arabid opsis. These genes confer female gametophytic phenotypes. FIS2 encodes a pr otein with a C2H2 zinc-finger moth and three putative nuclear localization signals, indicating that it is likely to be a transcription factor. FIS1 en codes a protein with homology to the Drosophila Polycomb group gene Enhance r-of-zeste and is identical to the recently described Arabidopsis gene MEDE A. FIS1 is a protein with a number of putative functional domains, includin g the SET domain present in Enhancer-of-zeste-related proteins. Comparison of the position of the lesions in the fis1 and medea mutant alleles indicat es that fis1 is a null allele producing a truncated polypeptide lacking all the protein domains whereas the deduced protein from medea lacks only the SET domain. We present a model of the role of FLS1 and FIS2 gene products i n seed development.