Regulation of Flowering Time and Floral Organ Identity by a MicroRNA and Its APETALA2-Like Target Genes Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc.016238.

MicroRNAs (miRNAs) are ∼21-nucleotide noncoding RNAs that have been identified in both animals and plants. Although in animals there is direct evidence implicating particular miRNAs in the control of developmental timing, to date it is not known whether plant miRNAs also play a role in regulating temporal transitions. Through an activation-tagging approach, we demonstrate that miRNA 172 (miR172) causes early flowering and disrupts the specification of floral organ identity when overexpressed in Arabidopsis. miR172 normally is expressed in a temporal manner, consistent with its proposed role in flowering time control. The regulatory target of miR172 is a subfamily of APETALA2 (AP2) transcription factor genes. We present evidence that miR172 downregulates these target genes by a translational mechanism rather than by RNA cleavage. Gain-of-function and loss-of-function analyses indicate that two of the AP2-like target genes normally act as floral repressors, supporting the notion that miR172 regulates flowering time by downregulating AP2-like target genes.

[1]  V. Ambros,et al.  The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14 , 1993, Cell.

[2]  F. Slack,et al.  The lin-41 RBCC gene acts in the C. elegans heterochronic pathway between the let-7 regulatory RNA and the LIN-29 transcription factor. , 2000, Molecular cell.

[3]  M. Mann,et al.  miRNPs: a novel class of ribonucleoproteins containing numerous microRNAs. , 2002, Genes & development.

[4]  T. Tuschl,et al.  Identification of Novel Genes Coding for Small Expressed RNAs , 2001, Science.

[5]  V. Ambros,et al.  The timing of lin-4 RNA accumulation controls the timing of postembryonic developmental events in Caenorhabditis elegans. , 1999, Developmental biology.

[6]  A. Pasquinelli,et al.  Genes and Mechanisms Related to RNA Interference Regulate Expression of the Small Temporal RNAs that Control C. elegans Developmental Timing , 2001, Cell.

[7]  B. Reinhart,et al.  Prediction of Plant MicroRNA Targets , 2002, Cell.

[8]  T. Tuschl,et al.  Identification of Tissue-Specific MicroRNAs from Mouse , 2002, Current Biology.

[9]  A. Pasquinelli,et al.  A Cellular Function for the RNA-Interference Enzyme Dicer in the Maturation of the let-7 Small Temporal RNA , 2001, Science.

[10]  V. Ambros,et al.  An Extensive Class of Small RNAs in Caenorhabditis elegans , 2001, Science.

[11]  Edwards Allen,et al.  P1/HC-Pro, a viral suppressor of RNA silencing, interferes with Arabidopsis development and miRNA unction. , 2003, Developmental cell.

[12]  C. Dean,et al.  Arabidopsis, the Rosetta stone of flowering time? , 2002, Science.

[13]  S. Hake,et al.  The control of maize spikelet meristem fate by the APETALA2-like gene indeterminate spikelet1. , 1998, Genes & Development.

[14]  D. Weigel,et al.  A thermosensory pathway controlling flowering time in Arabidopsis thaliana , 2003, Nature Genetics.

[15]  K. Taira,et al.  Hes1 is a target of microRNA-23 during retinoic-acid-induced neuronal differentiation of NT2 cells , 2003, Nature.

[16]  B. Reinhart,et al.  A biochemical framework for RNA silencing in plants. , 2003, Genes & development.

[17]  V. Ambros,et al.  The lin-4 regulatory RNA controls developmental timing in Caenorhabditis elegans by blocking LIN-14 protein synthesis after the initiation of translation. , 1999, Developmental biology.

[18]  R. Dixon,et al.  Activation tagging in Arabidopsis. , 2000, Plant physiology.

[19]  C. Llave,et al.  Cleavage of Scarecrow-like mRNA Targets Directed by a Class of Arabidopsis miRNA , 2002, Science.

[20]  M. Van Montagu,et al.  The AP2 domain of APETALA2 defines a large new family of DNA binding proteins in Arabidopsis. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[21]  C. Cogoni,et al.  RNA-mediated gene silencing , 2003, Cellular and Molecular Life Sciences CMLS.

[22]  Animesh Ray,et al.  DICER-LIKE1: blind men and elephants in Arabidopsis development. , 2002, Trends in plant science.

[23]  G. Hannon,et al.  C . elegans involved in developmental timing in Dicer functions in RNA interference and in synthesis of small RNA , 2001 .

[24]  S. Moose,et al.  Glossy15, an APETALA2-like gene from maize that regulates leaf epidermal cell identity. , 1996, Genes & development.

[25]  Xuemei Chen,et al.  A MicroRNA as a Translational Repressor of APETALA2 in Arabidopsis Flower Development , 2004, Science.

[26]  J. Bowman,et al.  Role of PHABULOSA and PHAVOLUTA in determining radial patterning in shoots , 2001, Nature.

[27]  S. Clough,et al.  Floral dip: a simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana. , 1998, The Plant journal : for cell and molecular biology.

[28]  J. Bowman,et al.  Genetic interactions among floral homeotic genes of Arabidopsis. , 1991, Development.

[29]  M. A. Rector,et al.  Endogenous and Silencing-Associated Small RNAs in Plants Online version contains Web-only data. Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc.003210. , 2002, The Plant Cell Online.

[30]  Michael T. McManus,et al.  Gene silencing using micro-RNA designed hairpins. , 2002, RNA.

[31]  L. Lim,et al.  An Abundant Class of Tiny RNAs with Probable Regulatory Roles in Caenorhabditis elegans , 2001, Science.

[32]  J. Messing,et al.  CARPEL FACTORY, a Dicer Homolog, and HEN1, a Novel Protein, Act in microRNA Metabolism in Arabidopsis thaliana , 2002, Current Biology.

[33]  Jna.  Note added in proof , 1980, The EMBO journal.

[34]  B. Reinhart,et al.  MicroRNAs in plants. , 2002, Genes & development.

[35]  Bruce A. Hay,et al.  The Drosophila MicroRNA Mir-14 Suppresses Cell Death and Is Required for Normal Fat Metabolism , 2003, Current Biology.

[36]  G. Ruvkun,et al.  Posttranscriptional regulation of the heterochronic gene lin-14 by lin-4 mediates temporal pattern formation in C. elegans , 1993, Cell.

[37]  C. Llave,et al.  P 1 / HC-Pro , a Viral Suppressor of RNA Silencing , Interferes with Arabidopsis Development and miRNA , 2003 .

[38]  R. Russell,et al.  bantam Encodes a Developmentally Regulated microRNA that Controls Cell Proliferation and Regulates the Proapoptotic Gene hid in Drosophila , 2003, Cell.

[39]  K. D. Kasschau,et al.  A MicroRNA as a Translational Repressor of APETALA 2 in Arabidopsis Flower Development , 2022 .

[40]  Javier F. Palatnik,et al.  Control of leaf morphogenesis by microRNAs , 2003, Nature.

[41]  V. Kim,et al.  MicroRNA maturation: stepwise processing and subcellular localization , 2002, The EMBO journal.

[42]  B. Reinhart,et al.  The 21-nucleotide let-7 RNA regulates developmental timing in Caenorhabditis elegans , 2000, Nature.

[43]  G. Hutvagner,et al.  A microRNA in a Multiple-Turnover RNAi Enzyme Complex , 2002, Science.