Journal
PLANT JOURNAL
Volume 65, Issue 6, Pages 922-935Publisher
WILEY
DOI: 10.1111/j.1365-313X.2010.04479.x
Keywords
ferredoxin; flavodoxin; complementation; photosynthesis; knock-down; transplastomic
Categories
Funding
- Agencia Nacional de Promocion Cientifica y Tecnologica, Argentina [PICT01-14648]
- Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Argentina [PID10777]
- Deutscher Akademischer Austauschdienst
Ask authors/readers for more resources
Ferredoxins are the main electron shuttles in chloroplasts, accepting electrons from photosystem I and delivering them to essential oxido-reductive pathways in the stroma. Ferredoxin levels decrease under adverse environmental conditions in both plants and photosynthetic micro-organisms. In cyanobacteria and some algae, this decrease is compensated for by induction of flavodoxin, an isofunctional flavoprotein that can replace ferredoxin in many reactions. Flavodoxin is not present in plants, but tobacco lines expressing a plastid-targeted cyanobacterial flavodoxin developed increased tolerance to environmental stress. Chloroplast-located flavodoxin interacts productively with endogenous ferredoxin-dependent pathways, suggesting that its protective role results from replacement of stress-labile ferredoxin. We tested this hypothesis by using RNA antisense and interference techniques to decrease ferredoxin levels in transgenic tobacco. Ferredoxin-deficient lines showed growth arrest, leaf chlorosis and decreased CO2 assimilation. Chlorophyll fluorescence measurements indicated impaired photochemistry, over-reduction of the photosynthetic electron transport chain and enhanced non-photochemical quenching. Expression of flavodoxin from the nuclear or plastid genome restored growth, pigment contents and photosynthetic capacity, and relieved the electron pressure on the electron transport chain. Tolerance to oxidative stress also recovered. In the absence of flavodoxin, ferredoxin could not be decreased below 45% of physiological content without fatally compromising plant survival, but in its presence, lines with only 12% remaining ferredoxin could grow autotrophically, with almost wild-type phenotypes. The results indicate that the stress tolerance conferred by flavodoxin expression in plants stems largely from functional complementation of endogenous ferredoxin by the cyanobacterial flavoprotein.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available