MATERNAL EFFECTS OF THE SHORT INTEGUMENT MUTATION ON EMBRYO DEVELOPMENT IN ARABIDOPSIS

Maternal gene products deposited in an animal egg determine the polari ty of embryonic axes and regulate embryonic cell-cell communication im portant for morphogenesis. Here we report the first maternal-effect em bryo-defective mutation discovered in a plant. Recessive mutations in the SHORT INTEGUMENT (SIN1) gene in Arabidopsis were previously shown to influence ovule development and flowering time. Here we show that a sin1 mutation has a pronounced maternal effect on zygotic embryo deve lopment. A homozygous sin1 mutant embryo is normal when nursed by a si n1/+ heterozygous maternal sporophyte. Strikingly, a sin1 or a sin1/embryo that is nursed by a sin1 homozygous maternal sporophyte develop s morphogenetic defects in the apical-basal and radial axes. The defec ts resemble those seen in some zygotic-effect embryonic pattern format ion mutants. These results imply that in maternal cells the SIN1 gene either codes for or controls the production of a diffusible morphogen necessary for proper zygotic embryogenesis. (C) 1996 Academic Press, I nc.