title: Cell Differentiation and Morphogenesis Are Uncoupled in Arabidopsis raspberry Embryos.
abstract: We identified two Arabidopsis embryo mutants, designated as raspberry1 and raspberry2, by screening T-DNA-mutagenized Arabidopsis lines. Embryogenesis in these mutants is indistinguishable from that of wild-type plants until the late-globular stage, after which raspberry1 and raspberry2 embryos fail to undergo the transition to heart stage, remain globular shaped, and proliferate an enlarged suspensor region. raspberry1 and raspberry2 embryo-proper regions enlarge during embryogenesis, become highly vacuolate, and display prominent convex, or "raspberry-like" protuberances on their outer cell layers. In situ hybridization studies with several embryo cell-specific mRNA probes indicated that the raspberry1 and raspberry2 embryo-proper regions differentiate tissue layers in their correct spatial contexts and that the regulation of cell-specific genes within these layers is normal. Surprisingly, a similar spatial and temporal pattern of mRNA accumulation occurs within the enlarged suspensor region of raspberry1 and raspberry2 embryos, suggesting that a defect in embryo-proper morphogenesis can cause the suspensor to take on an embryo-proper-like state and differentiate a radial tissue-type axis. We conclude that cell differentiation can occur in the absence of both organ formation and morphogenesis during plant embryogenesis and that interactions occur between the embryo-proper and suspensor regions.
authors.affiliation: Department of Biology, University of California, Los Angeles, California 90024-1606.
authors.forename: R.
authors.initials: R
authors.lastname: Yadegari
authors.forename: GRd.
authors.initials: G
authors.lastname: Paiva
authors.forename: T.
authors.initials: T
authors.lastname: Laux
authors.forename: A. M.
authors.initials: AM
authors.lastname: Koltunow
authors.forename: N.
authors.initials: N
authors.lastname: Apuya
authors.forename: J. L.
authors.initials: JL
authors.lastname: Zimmerman
authors.forename: R. L.
authors.initials: RL
authors.lastname: Fischer
authors.forename: J. J.
authors.initials: JJ
authors.lastname: Harada
authors.forename: R. B.
authors.initials: RB
authors.lastname: Goldberg