RT Journal Article
SR Electronic
T1 Mehler-Peroxidase Reaction Mediates Zeaxanthin Formation and Zeaxanthin-Related Fluorescence Quenching in Intact Chloroplasts
JF Plant Physiology
JO Plant Physiol.
FD American Society of Plant Biologists
SP 1354
OP 1361
DO 10.1104/pp.99.4.1354
VO 99
IS 4
A1 Neubauer, Christian
A1 Yamamoto, Harry Y.
YR 1992
UL http://www.plantphysiol.org/content/99/4/1354.abstract
AB Induction of zeaxanthin formation and the associated nonphotochemical quenching in iodoacetamide-treated, non-CO2-fixing intact chloroplasts of Lactuca sativa L. cv Romaine is reported. The electron transport needed to generate the required ΔpH for zeaxanthin formation and nonphotochemical quenching are ascribed to the Mehler-ascorbate peroxidase reaction. KCN, an inhibitor of ascorbate peroxidase, significantly affected these activities without affecting linear electron transport to methyl viologen or violaxanthin deepoxidase activity. At 1 millimolar KCN, zeaxanthin formation and ΔpH were inhibited 60 and 55%, respectively, whereas ascorbate peroxidase activity was inhibited almost totally. The KCN-resistant activity, which apparently was due to electron transport mediated by the Mehler reaction alone, however, was insufficient to support a high level of nonphotochemical quenching. We suggest that in vivo, as CO2 fixation becomes limiting, the Mehler-peroxidase reaction protects photosystem II against the excess light by supporting the electron transport needed for zeaxanthin-dependent nonphotochemical quenching and concomitantly scavenging H2O2. Ascorbate is essential for this process to occur.