miR172 regulates stem cell fate and defines the inner boundary of APETALA3 and PISTILLATA expression domain in Arabidopsis floral meristems.

In Arabidopsis, two floral homeotic genes APETALA2 (AP2) and AGAMOUS (AG) specify the identities of perianth and reproductive organs, respectively, in flower development. The two genes act antagonistically to restrict each other to their proper domains of action within the floral meristem. In addition to AG, which antagonizes AP2, miR172, a microRNA, serves as a negative regulator of AP2. In this study, we showed that AG and miR172 have distinct functions in flower development and that they largely act independently in the negative regulation of AP2. We uncovered functions of miR172-mediated repression of AP2 in the regulation of floral stem cells and in the delineation of the expression domain of another class of floral homeotic genes. Given the antiquity of miR172 in land plants, our findings have implications for the recruitment of a microRNA in the building of a flower in evolution.

[1]  Xuemei Chen,et al.  HEN1 functions pleiotropically in Arabidopsis development and acts in C function in the flower. , 2002, Development.

[2]  Neff Walker,et al.  A MicroRNA as a Translational Repressor of APETALA2 in Arabidopsis Flower Development , 2004 .

[3]  Elliot M. Meyerowitz,et al.  The homeotic gene APETALA3 of Arabidopsis thaliana encodes a MADS box and is expressed in petals and stamens , 1992, Cell.

[4]  A. Litt.  An Evaluation of A‐Function: Evidence from the APETALA1 and APETALA2 Gene Lineages , 2007, International Journal of Plant Sciences.

[5]  Hong Ma,et al.  Ectopic expression of the floral homeotic gene AGAMOUS in transgenic Arabidopsis plants alters floral organ identity , 1992, Cell.

[6]  J. Fletcher,et al.  Molecular mechanisms of flower development: an armchair guide , 2005, Nature Reviews Genetics.

[7]  L. Sieburth,et al.  Molecular dissection of the AGAMOUS control region shows that cis elements for spatial regulation are located intragenically. , 1997, The Plant cell.

[8]  D. Weigel,et al.  A Molecular Link between Stem Cell Regulation and Floral Patterning in Arabidopsis , 2001, Cell.

[9]  Hajime Sakai,et al.  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. , 2003, The Plant Cell Online.

[10]  D. Weigel,et al.  SUPERMAN, a regulator of floral homeotic genes in Arabidopsis. , 1992, Development.

[11]  S. Clark,et al.  Cell signalling at the shoot meristem , 2001, Nature Reviews Molecular Cell Biology.

[12]  M. Van Montagu,et al.  Control of Arabidopsis flower and seed development by the homeotic gene APETALA2. , 1994, The Plant cell.

[13]  Hong Ma,et al.  The protein encoded by the Arabidopsis homeotic gene agamous resembles transcription factors , 1990, Nature.

[14]  J. Bowman,et al.  Negative regulation of the Arabidopsis homeotic gene AGAMOUS by the APETALA2 product , 1991, Cell.

[15]  Cindy Gustafson-Brown,et al.  Molecular characterization of the Arabidopsis floral homeotic gene APETALA1 , 1992, Nature.

[16]  V. Sharma,et al.  Maintenance of stem cell populations in plants , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[17]  M. Lenhard,et al.  Termination of Stem Cell Maintenance in Arabidopsis Floral Meristems by Interactions between WUSCHEL and AGAMOUS , 2001, Cell.

[18]  D. Bartel,et al.  Antiquity of MicroRNAs and Their Targets in Land Plantsw⃞ , 2005, The Plant Cell Online.

[19]  T. Jack.  Molecular and Genetic Mechanisms of Floral Control , 2004, The Plant Cell Online.

[20]  Heiko Schoof,et al.  The Stem Cell Population of Arabidopsis Shoot Meristems Is Maintained by a Regulatory Loop between the CLAVATA and WUSCHEL Genes , 2000, Cell.

[21]  E. Meyerowitz,et al.  Function and regulation of the Arabidopsis floral homeotic gene PISTILLATA. , 1994, Genes & development.

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

[23]  J L Bowman,et al.  Genes directing flower development in Arabidopsis. , 1989, The Plant cell.

[24]  J. Bowman,et al.  Expression of the Arabidopsis floral homeotic gene AGAMOUS is restricted to specific cell types late in flower development. , 1991, The Plant cell.

[25]  D. Weigel,et al.  A genetic framework for floral patterning , 1998, Nature.

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

[27]  M. Hobe,et al.  Functional domains in plant shoot meristems , 2001, BioEssays : news and reviews in molecular, cellular and developmental biology.

[28]  J. Levin,et al.  UFO: an Arabidopsis gene involved in both floral meristem and floral organ development. , 1995, The Plant cell.

[29]  T. Laux,et al.  APETALA2 Regulates the Stem Cell Niche in the Arabidopsis Shoot Meristem[W] , 2005, The Plant Cell Online.

[30]  E. Meyerowitz,et al.  CLAVATA1, a regulator of meristem and flower development in Arabidopsis. , 1993, Development.