DOI: 10.1007/s10535-012-0235-7 BIOLOGIA PLANTARUM 57 (1): 159-163, 2013 159 BRIEF COMMUNICATION Water deficit and recovery response of Medicago truncatula plants expressing the ELIP-like DSP22 S.S. ARAÚJO 1,2 *, A.S. DUQUE 1 , J.M. SILVA 3,4 , D. SANTOS 2 , A.B. SILVA 3,4 and P. FEVEREIRO 1,3 Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2781-901 Oeiras, Portugal 1 Instituto de Investigação Científica e Tropical, Faculdade de Medicina Veterinária, 1300-477 Lisboa, Portugal 2 Departamento de Biologia Vegetal 3 and BioFIG 4 , Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal Abstract In this article, we present the response of Medicago truncatula Gaert. cv. Jemalong plants expressing constitutively the Dsp22 gene from Craterostigma plantagineum to water stress and rehydration. The Dsp22 gene encodes an ELIP-like protein thought to protect the chloroplast against photooxidative damage during the dehydration and rehydration. The Dsp22 transgenic homozygous M. truncatula plants showed higher amount of chlorophyll (Chl), lower Chl a/Chl b ratio and higher actual efficiency of energy conversion in photosystem 2 (Φ PSII ) after rehydration when compared to the wild type. The combined data from the Chl a fluorescence analysis, pigment quantification, and biomass accumulation showed that transgenic M. truncatula plants are able to recover from water deprivation better than wild type plants. Additional key words: abiotic stress, barrel medic, chlorophyll content, chlorophyll fluorescence, relative water content, transgenic plants. ⎯⎯⎯⎯ Improvement of plant responses to water deficit (WD) remains an open field of research especially in the legume family in which efforts have not kept pace with those described for cereals (Jeuffroy and Ney 1997). Medicago truncatula Gaert., commonly known as barrel medic, emerged as a model plant to investigate the basis of nitrogen fixation and nodulation, plant development, abiotic stress responses, population genetics, and structural genomics (reviewed in Ané et al. 2008, Rose 2008). M. truncatula is amenable to genetic trans- formation and different strategies based on genetic engineering can be set up to design lines with improved WD tolerance. It is well known that the stomatal limitation on photosynthesis imposed by the earlier stages of WD results in a decrease of primary electron acceptors available for photochemistry (Chaves 1991). If protection mechanisms are not activated, the excess of absorbed energy may induce photooxidative damage in chloroplast structures. To cope with the environmental stresses, plants activate a large set of genes which lead to the accumulation of specific stress-associated proteins (reviewed in Hussain et al. 2011). Early light inducible proteins (ELIPs) and ELIP-like proteins are described as pigment-binding components of thylakoid membranes that accumulate in response to various stresses (for ⎯⎯⎯⎯ Received 24 March 2011, accepted 30 January 2012. Abbreviations: Chl - chlorophyll; DSP22 - desiccation stress protein (22 kDa); ELIPs - early light induced proteins; F v /F m - variable to maximum Chl fluorescence ratio (maximum quantum efficiency of photosystem 2); LA - leaf blade area; LHC 2 - light harvesting complexes of the photosystem 2; PAR - photosynthetically active radiation; PSII - photosystem II; qN - non-photochemical quenching; qP - photochemical quenching; RWC - relative water content; SWC - soil water content; WD - water deficit; WDR - water deficit recovery; WW - well watered; Φ PSII - actual efficiency of energy conversion in photosystem II. Acknowledgements: We thank Prof. D. Bartels (IMBIO, Germany) for kindly providing the Dsp22 cDNA clone from Craterostigma plantagineum, Dr. V. Gemas (ITQB, Portugal) for support in statistical analysis and Dr A.M. De Almeida (IICT, Portugal) for critically reviewing the manuscript. This research was supported by Fundação para a Ciência e Tecnologia (Lisbon, Portugal), in the form of fellowships (S.S. Araújo BD/5225/2001 and Ciência 2008 Research Contract; A.S. Duque BPD/74784/2010, and D. Santos BPD/21968/2005 and Ciência 2007 Research Contract) and research project POCTI/BIO/56659/2004. * Corresponding author: fax: (+351) 214411277, e-mail: saraujo@itqb.unl.pt