Correlation between ferredoxin NADP+ reductase expression and oxidative stress in vascular plants

TOGNETTI, V.B.; PALATNIK,J.F.; POLI,H.O; BLANCO,N.E.; VALLE,E.M.; CARRILLO,N.

Rosario

Congreso; XIX ANNUAL MEETING OF ROSARIO BIOLOGY SOCIETY; 1999

Sociedad de Biologia de Rosario

The enzyme FNR is a thylakoid membrane-bound enzyme, which catalyzes NADP+ photoreducton in chloroplast. Different environmental stresses generate the accumulation of NADPH in the stromal fraction of chloroplasts and the derivation of electron to oxygen with production of superoxide anion radical  in situ. When plants were subjected to oxidative stress, FNR was released into the chloroplast stroma and consequently, it was converted into an NADPH consumer enzyme (Palatnik, et al., Plant Physiol 1997,115:1721-27), contributing to the antioxidante defense of the cell. To evaluate the extent of this contribution, transgenic tobacco plants expressing antisense mRNA for FNR were studied (seeds kindly providesd by Dr. U. Sonnewald, Gatersleben, Germany) Plants containing FNR levesl corresponding to 5% to 35% of the wild-type amounts were anlyzed for pigment content, photosynthetic capacity and lipid peroxidation. The results showed a positive correlation between each parameter and the FNR content. However, transgenic plants with lower FNR levles showed higher ratios of Chla/Chlb and lower ratios of Chla/carotene. The results obtained indicate that plants with reduced FNR levels also ahve lower amounts of light-harvesting complexes and electron transport components. The role of FNR in the global cell response to oxidative stress is discussed in the light of these observations.