title: Establishing leaf polarity: the role of small RNAs and positional signals in the shoot apex.
abstract: The flattening of leaves results from the juxtaposition of upper (adaxial) and lower (abaxial) domains in the developing leaf primordium. The adaxial-abaxial axis reflects positional differences in the leaf relative to the meristem and is established by redundant genetic pathways that interpret this asymmetry through instructive, possibly non-cell autonomous, signals. Small RNAs have been found to play a crucial role in this process, and specify mutually antagonistic fates. Here, we review both classical and recently-discovered factors that contribute to leaf polarity, as well as the candidate positional signals that their existence implies.
authors.affiliation: Cold Spring Harbor Laboratory, One Bungtown Road, Cold Spring Harbor, NY 11724, USA.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Chitwood
authors.forename: Mengjuan
authors.initials: M
authors.lastname: Guo
authors.forename: Fabio T S
authors.initials: FT
authors.lastname: Nogueira
authors.forename: Marja C P
authors.initials: MC
authors.lastname: Timmermans
mesh_terms: D016764:Cell Polarity; D018506:Gene Expression Regulation, Plant; D035683:MicroRNAs / Q000502:physiology; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology*; D018520:Plant Shoots / Q000254:growth & development / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D035683:MicroRNAs