Several recent studies have demonstrated that the expression of a cyanobacterial flavodoxin in plants can provide tolerance to a wide range of environmental stresses. Indeed, this strategy has been proposed as a potentially powerful biotechnological tool to generate multiple-tolerant crops. To determine whether flavodoxin expression specifically increased tolerance to salt stress and whether it might also preserve legume nitrogen fixation under saline conditions, the flavodoxin gene was introduced into the model legume Medicago truncatula. Expression of flavodoxin did not confer saline tolerance to the whole plant, although the sensitive nitrogen-fixing activity was maintained under salt stress in flavodoxin-expressing plants. Our results indicate that flavodoxin induced small but significant changes in the enzymatic activities involved in the nodule redox balance that might be responsible for the positive effect on nitrogen fixation. Expression of flavodoxin can be regarded as a potential tool to improve legume symbiotic performance under salt stress, and possibly other environmental stresses.

This work was supported by the Comunidad de Madrid (postdoctoral contract to T.C.P., and grants to M.M.L. and J.J.P.), the Consejo Superior de Investigaciones Cientı´ficas (CSIC) and the European Social Fund (postdoctoral contract to T.C.P. and a fellowship to F.J.R.), the Spanish Ministry of Education and Science, Fundacio´ n Areces and Junta de Comunidades de Castilla-La Mancha (grants to J.J.P.). The authors thank Dr. N. Carrillo for the kind gift of the pFLX plasmid.

12 pages, figures, and tables statistics.

Peer reviewed