The chloroplast small heat-shock protein: Evidence for a general role in protecting photosystem II against oxidative stress and photoinhibition

We have recently shown that the chloroplast small heat-shock protein (chlps Hsp) protects oxygen evolution and electron transport of Photosystem II dur ing heat stress, bur it is not known if the chlpsHsp protects Photosystem I I during other stresses. Here we show that the chlpsHsp was produced in viv a in leaves of Chenopodium album (L.) and Lycopersicum esculentum (Mill.) p lants subjected to drought (in high light, but not in low light), ultraviol et-A radiation, exogenous abscisic acid treatment, and oxidative stress (in duced by methyl viologen). Cold-shock treatment failed to induce the chlpsH sp in either species. Using an in vitro antibody-inhibition assay specific to the chlpsHsp, we provide evidence that the chlpsHsp can protect Photosys tem II electron transport from oxidative stress (induced by H2O2) and under conditions of photoinhibitory high light. These results indicate that the chlpsHsp plays a general role in the protection of Photosystem II against o xidative stress and photoinhibition.