title: Organ polarity in plants is specified through the opposing activity of two distinct small regulatory RNAs.
abstract: Small RNAs and their targets form complex regulatory networks that control cellular and developmental processes in multicellular organisms. In plants, dorsoventral (adaxial/abaxial) patterning provides a unique example of a developmental process in which early patterning decisions are determined by small RNAs. A gradient of microRNA166 on the abaxial/ventral side of the incipient leaf restricts the expression of adaxial/dorsal determinants. Another class of small RNAs, the TAS3-derivated trans-acting short-interfering RNAs (ta-siRNAs), are expressed adaxially and repress the activity of abaxial factors. Loss of maize leafbladeless1 (lbl1) function, a key component of the ta-siRNA biogenesis pathway, leads to misexpression of miR166 throughout the initiating leaf, implicating ta-siRNAs in the spatiotemporal regulation of miR166. The spatial restriction of tasiRNA biogenesis components suggests that this pathway may act non-cell-autonomously in the meristem and possibly contributes to the classic meristem-borne adaxializing Sussex signal. Here, we discuss the key participants in adaxial/abaxial patterning and point out the intriguing possibility that organ polarity in plants is established by the opposing action of specific ta-siRNAs and miRNAs.
authors: Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
authors: F T S
authors: FT
authors: Nogueira
authors: A K
authors: AK
authors: Sarkar
authors: D H
authors: DH
authors: Chitwood
authors: M C P
authors: MC
authors: Timmermans
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development; D019521:Body Patterning / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D063245:Plant Development; D018515:Plant Leaves / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics; D010944:Plants / Q000235:genetics*; D018749:RNA, Plant / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics
chemical_list: D035683:MicroRNAs; D010940:Plant Proteins; D018749:RNA, Plant; D034741:RNA, Small Interfering