title: An Interplay Between Small Regulatory RNAs Patterns Leaves.
abstract: Adaxial/abaxial (dorsoventral) leaf polarity is a unique example of a developmental process in which early patterning decisions are determined by small regulatory RNAs. In maize, an abaxial gradient of the microRNA miR166 in the incipient leaf defines the localization of HD-ZIPIII transcripts that promote adaxial identity. Loss of leafbladeless1 (lbl1) function, necessary for the biogenesis of TAS3-derived trans-acting short-interfering RNAs (ta-siRNAs), leads to ectopic accumulation of miR166 throughout the initiating leaf. These findings indicate that the TAS3 ta-siRNA pathway specifies leaf polarity by spatially restricting miR166 to the abaxial side. Here, we briefly discuss possible mechanisms by which the TAS3 ta-siRNA pathway could regulate miR166 expression. Such regulatory mechanisms likely involve AUXIN RESPoNSE FACToRS and the phytohormone auxin. The convergence of small RNAs, and perhaps auxin, on key determinants of adaxial/abaxial organ polarity implicates them as candidate mobile signals that act at the plant apex to relay positional information from the meristem to the initiating leaf.
authors.affiliation: Cold Spring Harbor Laboratory; Cold Spring Harbor, New York USA.
authors.forename: Fabio Ts
authors.initials: FTs
authors.lastname: Nogueira
authors.forename: Marja Cp
authors.initials: MC
authors.lastname: Timmermans
references.citation: Curr Biol. 2006 May 9;16(9):939-44
references.pmid: 16682356
references.citation: Nature. 2004 Mar 4;428(6978):84-8
references.pmid: 14999285
references.citation: Genes Dev. 2003 Jan 1;17(1):49-63
references.pmid: 12514099
references.citation: Genes Dev. 2004 Oct 1;18(19):2368-79
references.pmid: 15466488
references.citation: Plant Cell. 2005 Aug;17(8):2157-71
references.pmid: 16006579
references.citation: Nat Genet. 2005 Dec;37(12):1356-60
references.pmid: 16273107
references.citation: Development. 2006 Aug;133(15):2973-81
references.pmid: 16818444
references.citation: Nat Cell Biol. 2003 Nov;5(11):939-43
references.pmid: 14593411
references.citation: Plant Cell. 2005 Nov;17(11):2899-910
references.pmid: 16199616
references.citation: Nature. 2004 Mar 4;428(6978):81-4
references.pmid: 14999284
references.citation: Genes Dev. 2007 Apr 1;21(7):750-5
references.pmid: 17403777
references.citation: Development. 1998 Aug;125(15):2813-23
references.pmid: 9655804
references.citation: Curr Biol. 2006 May 9;16(9):927-32
references.pmid: 16682354
references.citation: Curr Biol. 2003 Oct 14;13(20):1768-74
references.pmid: 14561401
references.citation: Plant J. 1999 Aug;19(3):309-19
references.pmid: 10476078
references.citation: Curr Biol. 2006 May 9;16(9):933-8
references.pmid: 16682355
references.citation: Nature. 2001 Jun 7;411(6838):709-13
references.pmid: 11395776
references.citation: Cell. 2005 Apr 22;121(2):207-21
references.pmid: 15851028
references.citation: Development. 2007 Mar;134(5):813-23
references.pmid: 17251271
references.citation: Development. 2004 Sep;131(18):4533-44
references.pmid: 15342478