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First published online September 8, 2006; 10.1104/pp.106.083543 Plant Physiology 142:972-983 (2006) © 2006 American Society of Plant Biologists
Isolation of mtpim Proves Tnt1 a Useful Reverse Genetics Tool in Medicago truncatula and Uncovers New Aspects of AP1-Like Functions in Legumes1Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, 46022 Valencia, Spain (R.B., C.F., J.P.B., L.A.C., F.M.); and Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, 91198 Gif sur Yvette cedex, France (I.d'E., V.C., A.K., P.R.)
Comparative studies help shed light on how the huge diversity in plant forms found in nature has been produced. We use legume species to study developmental differences in inflorescence architecture and flower ontogeny with classical models such as Arabidopsis thaliana or Antirrhinum majus. Whereas genetic control of these processes has been analyzed mostly in pea (Pisum sativum), Medicago truncatula is emerging as a promising alternative system for these studies due to the availability of a range of genetic tools. To assess the use of the retrotransposon Tnt1 for reverse genetics in M. truncatula, we screened a small Tnt1-mutagenized population using degenerate primers for MADS-box genes, known controllers of plant development. We describe here the characterization of mtpim, a new mutant caused by the insertion of Tnt1 in a homolog to the PROLIFERATING INFLORESCENCE MERISTEM (PIM)/APETALA1 (AP1)/SQUAMOSA genes. mtpim shows flower-to-inflorescence conversion and altered flowers with sepals transformed into leaves, indicating that MtPIM controls floral meristem identity and flower development. Although more extreme, this phenotype resembles the pea pim mutants, supporting the idea that M. truncatula could be used to complement analysis of reproductive development already initiated in pea. In fact, our study reveals aspects not shown by analysis of pea mutants: that the mutation in the AP1 homolog interferes with the specification of floral organs from common primordia and causes conversion of sepals into leaves, in addition to true conversion of flowers into inflorescences. The isolation of mtpim represents a proof of concept demonstrating that Tnt1 populations can be efficiently used in reverse genetics screenings in M. truncatula.
1 This work was supported by the Secretaría General del Plan Nacional de Investigación Científica y Desarrollo Tecnológico (Spain; grant no. BIO2000–0940), the Generalitat Valenciana (grant no. GV–03–66), and the European Union Grain Legumes Integrated Project (grant no. FP6–2002–FOOD–1–506223). R.B. was supported by a fellowship of the Ministerio de Educación y Ciencia (Spain); I.d'E. was supported by a French Ministère de l'Education Nationale, de la Recherche et de la Technologie fellowship and the European Union Medicago Project (grant no. QLG2–CT–2000–00676). 2 Present address: Laboratories Physiologie Cellulaire Végétale, UMR CNRS 5168-CEA-INRA1200-UJF, 17 Av des Martyrs, bât.c2, 38054 Grenoble cedex, France. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Francisco Madueño (madueno{at}ibmcp.upv.es). www.plantphysiol.org/cgi/doi/10.1104/pp.106.083543 * Corresponding author; e-mail madueno{at}ibmcp.upv.es; fax 34–963877859. Received May 18, 2006; accepted August 7, 2006; published September 8, 2006. This article has been cited by other articles:
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