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Full-Size ABC Transporters from the ABCG Subfamily in Medicago truncatula

¹Institute of Bioorganic Chemistry PAS, Noskowskiego 12/14, 61-704 Poznań, Poland; ²Institute of Computing Science, Poznań Institute of Technology, Piotrowo 2, 60-965 Poznań, Poland; ³Department of Plant Biotechnology, Faculty of Natural Science, University of Szczecin, Waska 13, 71-415 Szczecin, Poland

Full-size ATP-binding cassette (ABC) transporters belonging to the ABCG subfamily are unique for plants and fungi. There is growing evidence that certain of these proteins play a role in plant defense or signaling systems. As yet, a complete set of full-size ABCG protein genes has been inventoried and classified in only two plants: Arabidopsis thaliana and Oryza sativa. Recently, a domain-based clustering analysis has predicted the presence of at least 12 genes encoding such proteins in the Lotus japonicus genome. Here, we identify and classify 19 genes coding full-size ABCG proteins in Medicago truncatula, a model legume plant. We have found that the majority of these genes are expressed in roots and flowers whereas only a few are expressed in leaves. Expression of several has been induced upon pathogenic infection in both roots and leaves. ABCG messenger RNAs have been detected in root nodules forming during symbiosis of legume plants and nitrogen-fixing bacteria. The data presented provide a scaffold for further studies of the physiological function of Medicago ABCG transporters and their possible role in modulating plant--microorganism interactions.