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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Differential Expression of the TFIIIA Regulatory Pathway in Response to Salt Stress between Medicago truncatula Genotypes^1,[W]

Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, F–91198 Gif-sur-Yvette cedex, France (L.d.L., F.M., S.B., F.F., M.C.); and Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Sevilla, 41012 Seville, Spain (L.d.L., F.M., M.M., C.S.)

Soil salinity is one of the most significant abiotic stresses for crop plants, including legumes. These plants can establish root symbioses with nitrogen-fixing soil bacteria and are able to grow in nitrogen-poor soils. Medicago truncatula varieties show diverse adaptive responses to environmental conditions, such as saline soils. We have compared the differential root growth of two genotypes of M. truncatula (108-R and Jemalong A17) in response to salt stress. Jemalong A17 is more tolerant to salt stress than 108-R, regarding both root and nodulation responses independently of the nitrogen status of the media. A dedicated macroarray containing 384 genes linked to stress responses was used to compare root gene expression during salt stress in these genotypes. Several genes potentially associated with the contrasting cellular responses of these plants to salt stress were identified as expressed in the more tolerant genotype even in the absence of stress. Among them, a homolog of the abiotic stress-related COLD-REGULATEDA1 gene and a TFIIIA-related transcription factor (TF), MtZpt2-1, known to regulate the former gene. Two MtZpt2 TFs (MtZpt2-1 and MtZpt2-2) were found in Jemalong A17 plants and showed increased expression in roots when compared to 108-R. Overexpression of these TFs in the sensitive genotype 108-R, but not in Jemalong A17, led to increased root growth under salt stress, suggesting a role for this pathway in the adaptive response to salt stress of these M. truncatula genotypes.

The author responsible for distribution of material integral to the findings presented in this article in accord with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Martin Crespi (crespi{at}isv.cnrs-gif.fr).

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.106146

^* Corresponding author; e-mail crespi{at}isv.cnrs-gif.fr.

Received July 24, 2007; accepted October 12, 2007; published October 19, 2007.