Julia Engelhorn1, Fanny Moreau1, Jennifer C Fletcher2, Cristel C Carles3. 1. Université Grenoble Alpes, UMR5168, F-38041 Grenoble, France CNRS, UMR5168, F-38054 Grenoble, France CEA, iRTSV, Laboratoire Physiologie Cellulaire et Végétale, F-38054 Grenoble, France INRA, F-38054 Grenoble, France. 2. Plant Gene Expression Center, USDA-ARS/University of California, Berkeley, 800 Buchanan Street, Albany, CA 94710, USA. 3. Université Grenoble Alpes, UMR5168, F-38041 Grenoble, France CNRS, UMR5168, F-38054 Grenoble, France CEA, iRTSV, Laboratoire Physiologie Cellulaire et Végétale, F-38054 Grenoble, France INRA, F-38054 Grenoble, France Cristel.carles@ujf-grenoble.fr.
Abstract
BACKGROUND AND AIMS: The morphological variability of the flower in angiosperms, combined with its relatively simple structure, makes it an excellent model to study cell specification and the establishment of morphogenetic patterns. Flowers are the products of floral meristems, which are determinate structures that generate four different types of floral organs before terminating. The precise organization of the flower in whorls, each defined by the identity and number of organs it contains, is controlled by a multi-layered network involving numerous transcriptional regulators. In particular, the AGAMOUS (AG) MADS domain-containing transcription factor plays a major role in controlling floral determinacy in Arabidopsis thaliana in addition to specifying reproductive organ identity. This study aims to characterize the genetic interactions between the ULTRAPETALA1 (ULT1) and LEAFY (LFY) transcriptional regulators during flower morphogenesis, with a focus on AG regulation. METHODS: Genetic and molecular approaches were used to address the question of redundancy and reciprocal interdependency for the establishment of flower meristem initiation, identity and termination. In particular, the effects of loss of both ULT1 and LFY function were determined by analysing flower developmental phenotypes of double-mutant plants. The dependency of each factor on the other for activating developmental genes was also investigated in gain-of-function experiments. KEY RESULTS: The ULT1 and LFY pathways, while both activating AG expression in the centre of the flower meristem, functioned independently in floral meristem determinacy. Ectopic transcriptional activation by ULT1 of AG and AP3, another gene encoding a MADS domain-containing flower architect, did not depend on LFY function. Similarly, LFY did not require ULT1 function to ectopically determine floral fate. CONCLUSIONS: The results indicate that the ULT1 and LFY pathways act separately in regulating identity and determinacy at the floral meristem. In particular, they independently induce AG expression in the centre of the flower to terminate meristem activity. A model is proposed whereby these independent contributions bring about a switch at the AG locus from an inactive to an active transcriptional state at the correct time and place during flower development.
BACKGROUND AND AIMS: The morphological variability of the flower in angiosperms, combined with its relatively simple structure, makes it an excellent model to study cell specification and the establishment of morphogenetic patterns. Flowers are the products of floral meristems, which are determinate structures that generate four different types of floral organs before terminating. The precise organization of the flower in whorls, each defined by the identity and number of organs it contains, is controlled by a multi-layered network involving numerous transcriptional regulators. In particular, the AGAMOUS (AG) MADS domain-containing transcription factor plays a major role in controlling floral determinacy in Arabidopsis thaliana in addition to specifying reproductive organ identity. This study aims to characterize the genetic interactions between the ULTRAPETALA1 (ULT1) and LEAFY (LFY) transcriptional regulators during flower morphogenesis, with a focus on AG regulation. METHODS: Genetic and molecular approaches were used to address the question of redundancy and reciprocal interdependency for the establishment of flower meristem initiation, identity and termination. In particular, the effects of loss of both ULT1 and LFY function were determined by analysing flower developmental phenotypes of double-mutant plants. The dependency of each factor on the other for activating developmental genes was also investigated in gain-of-function experiments. KEY RESULTS: The ULT1 and LFY pathways, while both activating AG expression in the centre of the flower meristem, functioned independently in floral meristem determinacy. Ectopic transcriptional activation by ULT1 of AG and AP3, another gene encoding a MADS domain-containing flower architect, did not depend on LFY function. Similarly, LFY did not require ULT1 function to ectopically determine floral fate. CONCLUSIONS: The results indicate that the ULT1 and LFY pathways act separately in regulating identity and determinacy at the floral meristem. In particular, they independently induce AG expression in the centre of the flower to terminate meristem activity. A model is proposed whereby these independent contributions bring about a switch at the AG locus from an inactive to an active transcriptional state at the correct time and place during flower development.
Authors: Cezary Smaczniak; Richard G H Immink; Jose M Muiño; Robert Blanvillain; Marco Busscher; Jacqueline Busscher-Lange; Q D Peter Dinh; Shujing Liu; Adrie H Westphal; Sjef Boeren; François Parcy; Lin Xu; Cristel C Carles; Gerco C Angenent; Kerstin Kaufmann Journal: Proc Natl Acad Sci U S A Date: 2012-01-11 Impact factor: 11.205
Authors: Wolfgang Busch; Andrej Miotk; Federico D Ariel; Zhong Zhao; Joachim Forner; Gabor Daum; Takuya Suzaki; Christoph Schuster; Sebastian J Schultheiss; Andrea Leibfried; Silke Haubeiss; Nati Ha; Raquel L Chan; Jan U Lohmann Journal: Dev Cell Date: 2010-05-18 Impact factor: 12.270
Authors: Cristel C Carles; Dan Choffnes-Inada; Keira Reville; Kvin Lertpiriyapong; Jennifer C Fletcher Journal: Development Date: 2005-01-26 Impact factor: 6.868