Overexpression of MtTdp2α (tyrosyl-DNA phosphodiesterase 2) gene confers salt tolerance in transgenic Medicago truncatula
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Soil salinity is one of the main abiotic stresses affecting yield in major crop plants, including legumes. Research carried out on model legumes such as barrel medic (Medicago truncatula Gaertn.) showed that the Tyrosyl-DNA phosphodiesterase 2α (MtTdp2α) DNA repair gene, involved in the removal of topoisomerase-DNA covalent complexes, play a key role in the plant response to osmotic and copper stresses. However, no informations are currently available about the involvement of MtTdp2α in response to salt stress and salt shock. In the present study we investigated the role of MtTdp2α under salinity (0, 50, 100, 150 and 200 mM NaCl) stress conditions in transgenic M. truncatula overexpressing the MtTdp2α gene. The level of salt tolerance of Tdp2-28 selected transgenic line was significantly higher than control as measured by the increase in shoot fresh weight, shoot dry weight and salt sensitivity index, in response to 100 mM NaCl. After salt stress, Tdp2-28 transgenic line showed significantly higher chlorophyll and carotenoid total contents, 2,2-Diphenyl-1-Picrylhydrazyl radical scavenging activity, and significantly lower levels of oxidative DNA damage than the control line. Interestingly, the expression levels of several genes, including genes linked to genome maintenance and regulation of DNA topology (MtTdp1α, MtTop2), base excision repair pathway (MtOGG1) and double strand break sensing/repair (MtMRE11) were enhanced in Tdp2-28 transgenic shoots under salt stress conditions as compared to their controls. These findings suggest that MtTdp2α play an important role in plant tolerance to salt stress.
Overexpression of MtTdp2α gene in Medicago truncatula confers salt stress tolerance through better plant growth performances, higher chlorophyll and carotenoid contents, increased antioxidant capacity, reduced oxidative DNA damage, and by up-regulation of several genes involved in DNA metabolism.
KeywordsMedicago truncatula Salt tolerance Transgenic Tyrosyl-DNA phosphodiesterase
Base excision repair
Double strand break
Salt sensitivity index
Quantitative real-time PCR
Murashige and Skoog (1962)
Reactive oxigen species
5-Tyrosyl DNA phosphodiesterase II
MC conceived and designed the research, conducted the salt stress, the pigment and antioxidant determination experiments and wrote the manuscript. LB, MC and AT performed molecular and ion determination analyses, and analyzed the data. All authors discussed the results and agreed to the final version of the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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