Short sequence paper Characterization of three Rop GTPase genes of alfalfa (Medicago sativa L.) Attila Szűcs a , Dulguun Dorjgotov a , Krisztina Ötvös a , Csilla Fodor a , Mónika Domoki a , János Györgyey a , Péter Kaló b,c , György B. Kiss b,c , Dénes Dudits a , Attila Fehér a, ⁎ a Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, Temesvári krt. 62., 6726 Szeged, Hungary b Institute of Genetics, Biological Research Center of the Hungarian Academy of Sciences, Temesvári krt. 62., 6726 Szeged, Hungary c Institute of Genetics, Agricultural Biotechnology Center, Szent-Györgyi A. u. 4., 2100 Gödöllő, Hungary Received 11 August 2005; received in revised form 3 March 2006; accepted 3 March 2006 Available online 29 March 2006 Abstract Three cDNA clones coding for Medicago sativa Rop GTPases have been isolated. The represented genes could be assigned to various linkage groups by genetic mapping. They were expressed in all investigated plant organs, although at different level. Relative gene expression patterns in response to Sinorhizobium infection of roots as well as during somatic embryogenesis indicated their differential participation in these processes. DNA sequences coding for altogether six different Medicago sp. Rop GTPases could be identified in sequence databases. Based on their homology to each other and to their Arabidopsis counterparts, a unified nomenclature is suggested for Medicago Rop GTPases. © 2006 Elsevier B.V. All rights reserved. Keywords: Gene expression; Genetic mapping; Medicago truncatula; Nod-factor; Plant Rho GTPase; Somatic embryogenesis; Sinorhizobium meliloti Eukaryotic cells synthesize a range of small (molecular mass 20–25 kDa) GTP-binding proteins with evolutionary conserved structure and wide functional diversity [1]. Rho- type GTPases form a distinct class within this GTP-binding protein family. They cycle between their active, GTP-bound, and inactive, GDP-bound, conformations and are involved in diverse signal transduction pathways. In order to fulfill their function, they have to interact with a plethora of proteins. Their protein partners include regulators of GTP/GDP- binding and GTPase activities as well as downstream effectors. Effectors of Rho GTPases mediate signals towards the cytoskeleton and to the plasma membrane NADPH oxidase complex but are also involved in the regulation of transcription [2]. Rho-type GTPase proteins are highly conserved from yeasts to human and seem to be indispensable for basic functioning of the eukaryotic cell. However, there are interesting differences among the various eukaryotic organisms in the representation of the Rho family. Animals have Rac-type GTPases in addition to Rho- and Cdc42-type proteins present in yeast cells [1], while plants possess only one unique Rho GTPase subfamily, named “Rho-of-plants” or Rop [3]. Considering the basic role of the plant cytoskeleton in plant development, as well as the potential significance of plasma- membrane NADPH oxidases in plant defense reactions, Rop GTPases have attracted a special interest during the last few years (for a recent review, [4]). Plant Rho-type GTPase cDNA clones have been isolated from many plant species including Arabidopsis (for review [3]), rice (for review [5]), tobacco [6], cotton [7,8], Lotus [9], as well as Medicago [10,11]. The characterization of Medicago Rop GTPases is limited only to few studies [10,11], although the involvement of Rop GTPases in nitrogen-fixing root nodule formation, mycorrhizal symbiosis or somatic embryogenesis, for example, could be well studied in this model organism. In order to isolate cDNA clones of alfalfa Rop GTPases, a cDNA library [12], made from 4-day-old root nodules induced by Sinorhizobium meliloti on alfalfa (Medicago sativa ssp. varia, line A2) roots, was screened by a full length maize Rho GTPase cDNA clone (Accession number: AF126055). Screening of approximately 10 6 individual phages resulted in around two hundreds of hybridizing Biochimica et Biophysica Acta 1759 (2006) 108 – 115 http://www.elsevier.com/locate/bba ⁎ Corresponding author. Fax: +36 62 433 434. E-mail address: fehera@brc.hu (A. Fehér). 0167-4781/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.bbaexp.2006.03.001