Control of fertilization-independent endosperm development by the MEDEA polycomb gene in Arabidopsis

Control of fertilization-independent endosperm development by the MEDEA polycomb gene in Arabidopsis

^*Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720; ^‡Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel; ^§Section of Plant Biology, Division of Biological Sciences, University of California, Davis, CA 95616; and ^¶Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, CA 90024-1606

Communicated by Brian A. Larkins, University of Arizona, Tuscon, AZ (received for review November 24, 1998)

Abstract

Higher plant reproduction is unique because two cells are fertilized in the haploid female gametophyte. Egg and sperm nuclei fuse to form the embryo. A second sperm nucleus fuses with the central cell nucleus that replicates to generate the endosperm, a tissue that supports embryo development. To understand mechanisms that initiate reproduction, we isolated a mutation in Arabidopsis, f644, that allows for replication of the central cell and subsequent endosperm development without fertilization. When mutant f644 egg and central cells are fertilized by wild-type sperm, embryo development is inhibited, and endosperm is overproduced. By using a map-based strategy, we cloned and sequenced the F644 gene and showed that it encodes a SET-domain polycomb protein. Subsequently, we found that F644 is identical to MEDEA (MEA), a gene whose maternal-derived allele is required for embryogenesis [Grossniklaus, U., Vielle-Calzada, J.-P., Hoeppner, M. A. & Gagliano, W. B. (1998) Science 280, 446–450]. Together, these results reveal functions for plant polycomb proteins in the suppression of central cell proliferation and endosperm development. We discuss models to explain how polycomb proteins function to suppress endosperm and promote embryo development.

Footnotes

↵ † T.K. and N.O. contributed equally to this work.
↵ ‖ To whom reprint requests should be addressed at: 111 Koshland Hall, University of California, Berkeley, CA 94720-3102. e-mail: rfischer{at}uclink4.berkeley.edu.
ABBREVIATION:

DAP,

days after pollination