Abstract
The photo-stability of photosystem I (PSI) is of high importance for the photosynthetic processes. For this reason, we studied the protective action of two biogenic polyamines (PAs) spermine (Spm) and spermidine (Spd) on PSI activity in isolated thylakoid membranes subjected to photoinhibition. Our results show that pre-loading thylakoid membranes with Spm and Spd reduced considerably the inhibition of O2 uptake rates, P700 photooxidation and the accumulation of superoxide anions (O2 −) induced by light stress. Spm seems to be more effective than Spd in preserving PSI photo-stability. The correlation of the extent of PSI protection, photosystem II (PSII) inhibition and O2 − generation with increasing Spm doses revealed that PSI photo-protection is assumed by two mechanisms depending on the PAs concentration. Given their antioxidant character, PAs scavenge directly the O2 − generated in thylakoid membranes at physiological concentration (1 mM). However, for non-physiological concentration, the ability of PAs to protect PSI is due to their inhibitory effect on PSII electron transfer.
Highlights
Plant productivity is highly dependent on the integrity of the photosynthetic apparatus
To investigate the effect of intense white light and two PAs on photosystem I (PSI) activity, the oxygen uptake rates were measured in isolated thylakoid membranes exposed to strong illumination in the absence or presence of Spm or Spd
This inhibition of O2 uptake indicated the perturbation of electron transport through the thylakoid membranes and the dysfunction of PSI complexes
Summary
Plant productivity is highly dependent on the integrity of the photosynthetic apparatus. Thylakoid membranes which are composed mainly of 4 supra-molecular protein complexes: photosystem II (PSII), photosystem I (PSI), cytochrome b6/f (Cyt b6/f) and ATP synthase. These complexes are responsible for the photochemical transformation of light energy into chemical energy resulting into the production of NADPH and ATP. Excitation of PSII with light produces electrons, protons and oxygen via water oxidation. The electrons are transferred to PSI through the transporters of the thylakoid membranes to reduce NADP+. The protons are used by ATP synthase for adenosine triphosphate (ATP) formation [1]. NADPH and ATP are used to assimilate CO2 for sugar production via Calvin-Benson cycle
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
