Relationship between stress tolerance and flavodoxin levels in transgenic tobacco plants

CECCOLI, R. D.; BLANCO, N. E.; SEGRETIN, M. E.; BRAVO-ALMONACID, F. F.; SCHEIBE, R.; HAJIREZAEI, M. R.; CARRILLO, N.

Puerto Madryn

Congreso; XLVI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

Ferredoxins (Fd) are iron-sulfur proteins involved in different one-electron transfer pathways. Fd levels decrease under adverse environmental conditions in photosynthetic organisms. In cyanobacteria, this decline is compensated by induction of flavodoxin (Fld), an isofunctional flavoprotein. Fld is absent in higher plants but transgenic Nicotiana tabacum lines accumulating Anabaena Fld in plastids displayed increased tolerance to oxidative stress. As the tolerance degree was correlated with Fld dose in plastids, the aim of this work is to evaluate whether the protective effect of Fld saturates above certain threshold of Fld content, if it continues to improve or if Fld overaccumulation becomes detrimental due to perturbation of redox homeostasis. Therefore, we prepared tobacco plants expressing Fld by transplastomic. Photosynthetic performance of plants with different Fld doses was evaluated under normal growth conditions. To estimate stress tolerance, these plants were exposed to methyl viologen, an herbicide which generates oxidative stress in chloroplasts. Photosynthesis efficiency, antioxidant and chlorophyll levels, and cellular damage were determined. Highest stress tolerance was observed in plants expressing 70 pmol Fld/g fw. Overaccumulation of Fld did not improve its protective effect; however, it did not affect negatively photosynthetic and metabolic performance.