Abstract

We have examined tobacco transformed with an antisense construct against the Rieske-FeS subunit of the cytochrome b(6)f complex, containing only 15 to 20% of the wild-type level of cytochrome f. The anti-Rieske FeS leaves had a comparable chlorophyll and Photosystem II reaction center stoichiometry and a comparable carotenoid profile to the wild-type, with differences of less than 10% on a leaf area basis. When exposed to high irradiance, the anti-Rieske-FeS leaves showed a greatly increased closure of Photosystem II and a much reduced capacity to develop non-photochemical quenching compared with wild-type. However, contrary to our expectations, the anti-Rieske-FeS leaves were not more susceptible to photoinhibition than were wild-type leaves. Further, when we regulated the irradiance so that the excitation pressure on photosystem II was equivalent in both the anti-Rieske-FeS and wild-type leaves, the anti-Rieske-FeS leaves experienced much less photoinhibition than wild-type. The evidence from the anti-Rieske-FeS tobacco suggests that rapid photoinactivation of Photosystem II in vivo only occurs when closure of Photosystem II coincides with lumen acidification. These results suggest that the model of photoinhibition in vivo occurring principally because of limitations to electron withdrawal from photosystem II does not explain photoinhibition in these transgenic tobacco leaves, and we need to re-evaluate the twinned concepts of photoinhibition and photoprotection.

Keywords

fluorescence quenching; photoprotection; redox signalling; xanthophyll cycle

Published in

Photosynthesis Research
1996, Volume: 50, number: 2, pages: 159-169
Publisher: KLUWER ACADEMIC PUBL

UKÄ Subject classification

Botany


Publication identifier

DOI: https://doi.org/10.1007/BF00014886

Permanent link to this page (URI)

https://res.slu.se/id/publ/76377