Transformation of shoots into roots in Arabidopsis embryos mutant at the TOPLESS locus.

We describe a novel phenotype in Arabidopsis embryos homozygous for the temperature-sensitive topless-1 mutation. This mutation causes the transformation of the shoot pole into a root. Developing topless embryos fail to express markers for the shoot apical meristem (SHOOT MERISTEMLESS and UNUSUAL FLORAL ORGANS) and the hypocotyl (KNAT1). By contrast, the pattern of expression of root markers is either duplicated (LENNY, J1092) or expanded (SCARECROW). Shifts of developing topless embryos between permissive and restrictive temperatures show that apical fates (cotyledons plus shoot apical meristem) can be transformed to basal fates (root) as late as transition stage. As the apical pole of transition stage embryos shows both morphological and molecular characteristics of shoot development, this demonstrates that the topless 1 mutation is capable of causing structures specified as shoot to be respecified as root. Finally, our experiments fail to show a clear link between auxin signal transduction and topless-1 mutant activity: the development of the apical root in topless mutant individuals is not dependent on the activity of the predicted auxin response factor MONOPTEROS nor is the expression of DR5, a proposed 'auxin maximum reporter', expanded in the apical domain of topless embryos.

[1]  M. Estelle,et al.  The axr6 mutants of Arabidopsis thaliana define a gene involved in auxin response and early development. , 2000, Development.

[2]  Ottoline Leyser,et al.  An Auxin-Dependent Distal Organizer of Pattern and Polarity in the Arabidopsis Root , 1999, Cell.

[3]  G. Jürgens,et al.  Coordinated polar localization of auxin efflux carrier PIN1 by GNOM ARF GEF. , 1999, Science.

[4]  M. Aida,et al.  Shoot apical meristem and cotyledon formation during Arabidopsis embryogenesis: interaction among the CUP-SHAPED COTYLEDON and SHOOT MERISTEMLESS genes. , 1999, Development.

[5]  G. Jürgens,et al.  The auxin-insensitive bodenlos mutation affects primary root formation and apical-basal patterning in the Arabidopsis embryo. , 1999, Development.

[6]  J. Long,et al.  The development of apical embryonic pattern in Arabidopsis. , 1998, Development.

[7]  J. R. McConnell,et al.  Leaf polarity and meristem formation in Arabidopsis. , 1998, Development.

[8]  G. Sandberg,et al.  High temperature promotes auxin-mediated hypocotyl elongation in Arabidopsis. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[9]  C. Hardtke,et al.  The Arabidopsis gene MONOPTEROS encodes a transcription factor mediating embryo axis formation and vascular development , 1998, The EMBO journal.

[10]  G. Hagen,et al.  ARF1, a transcription factor that binds to auxin response elements. , 1997, Science.

[11]  H Fujisawa,et al.  Genes involved in organ separation in Arabidopsis: an analysis of the cup-shaped cotyledon mutant. , 1997, The Plant cell.

[12]  Detlef Weigel,et al.  A LEAFY co-regulator encoded by UNUSUAL FLORAL ORGANS , 1997, Current Biology.

[13]  P. Benfey,et al.  The SCARECROW Gene Regulates an Asymmetric Cell Division That Is Essential for Generating the Radial Organization of the Arabidopsis Root , 1996, Cell.

[14]  P. Perez,et al.  AINTEGUMENTA, an APETALA2-like gene of Arabidopsis with pleiotropic roles in ovule development and floral organ growth. , 1996, The Plant cell.

[15]  June I. Medford,et al.  A member of the KNOTTED class of homeodomain proteins encoded by the STM gene of Arabidopsis , 1996, Nature.

[16]  Jonathan D. G. Jones,et al.  Patterns of gene action in plant development revealed by enhancer trap and gene trap transposable elements. , 1995, Genes & development.

[17]  S. Hake,et al.  A knotted1-like homeobox gene in Arabidopsis is expressed in the vegetative meristem and dramatically alters leaf morphology when overexpressed in transgenic plants. , 1994, The Plant cell.

[18]  D. Meinke,et al.  Embryogenic transformation of the suspensor in twin, a polyembryonic mutant of Arabidopsis. , 1994, Developmental biology.

[19]  C. Gillmor,et al.  EMB30 is essential for normal cell division, cell expansion, and cell adhesion in Arabidopsis and encodes a protein that has similarity to Sec7 , 1994, Cell.

[20]  R. Poethig,et al.  Formation of the shoot apical meristem in Arabidopsis thaliana: an analysis of development in the wild type and in the shoot meristemless mutant , 1993 .

[21]  E. Meyerowitz,et al.  Arabidopsis ethylene-response gene ETR1: similarity of product to two-component regulators. , 1993, Science.

[22]  B. Scheres,et al.  Cellular organisation of the Arabidopsis thaliana root. , 1993, Development.

[23]  F. Ausubel,et al.  A procedure for mapping Arabidopsis mutations using co-dominant ecotype-specific PCR-based markers. , 1993, The Plant journal : for cell and molecular biology.

[24]  N. Chua,et al.  Auxin Polar Transport Is Essential for the Establishment of Bilateral Symmetry during Early Plant Embryogenesis. , 1993, The Plant cell.

[25]  G. Jürgens,et al.  Apical-basal pattern formation in the Arabidopsis embryo: studies on the role of the gnom gene , 1993 .

[26]  S. Mansfield,et al.  Early embryogenesis in Arabidopsis thaliana. II. The developing embryo , 1991 .

[27]  S. Mansfield,et al.  Early embryogenesis in Arabidopsis thaliana. I, The mature embryo sac , 1991 .

[28]  W. Gelbart,et al.  The relationship of decapentaplegic and engrailed expression in Drosophila imaginal disks: do these genes mark the anterior-posterior compartment boundary? , 1991, Development.

[29]  M. Estelle,et al.  Insensitivity to Ethylene Conferred by a Dominant Mutation in Arabidopsis thaliana , 1988, Science.

[30]  P. Walker.  Cellular Organization , 1961, Nature.