CHANGES IN THE THYLAKOID PROTEIN PATTERN IN SUNFLOWER PLANTS AS A RESULT OF OZONE FUMIGATION

The effect of fumigation of sunflower plants with 150 nl L-1 of ozone (4 h a day for 4 days) on photosynthetic electron transfer and thylako id polypeptide pattern has been studied. Ozone affects both PSI and PS II. By immunoblotting analysis, a loss of steady state level of the PS II reaction centre D1 protein was observed, the extent of which was co mparable with the loss of electron transfer. Pulse-labelling experimen ts carried out during the last part of fumigation (either during the l ast 4h or 15 min) indicated that, as far as incorporation of radioacti ve methionine on D1 is concerned, fumigation impairs the synthesis of this protein. In conclusion, ozone induces an alteration in photosynth etic electron transport functionality, probably due to a disorganizati on in the thylakoid complexes, as a direct action on polypeptides and an impairment in protein synthesis at che PSI and PSII levels, in part icular its toxic effect may have altered D1 protein turnover, so decre asing its in vivo synthesis.