Oxidative damage to thylakoid proteins in water-stressed leaves of wheat (Triticum aestivum L.).

TAMBUSSI EDUARDO ALBERTO; BARTOLI CARLOS GUILLERMO; BELTRANO JOSÉ; GUIAMET JUAN JOSÉ; ARAUS JOSÉ LUIS

PHYSIOLOGIA PLANTARUM

Blackwell Publishing

Año: 2000 vol. 108 p. 398 - 404

0031-9317

The production of reactive oxygen species in the chloroplast may increase under water deficit. To determine if this causes oxidative damage to the photosynthetic apparatus, we analyzed the accumulation of oxidatively damaged proteins in thylakoids of water-stressed wheat (Triticum aesti7um L.) leaves. Water stress was imposed on 4-week-old plants by withholding watering for 10 days to reach a soil water potential of about -2.0 MPa. In thylakoids of water-stressed leaves there was an increase in oxidative damage, particularly in polypeptides of 68, 54, 41 and 24 kDa. High molecular mass oxidized (probably cross-linked) proteins accumulated in chloroplasts of droughted leaves. Oxidative damage was associated with a substantial decrease in photosynthetic electron transport activity and photosystem II (PSII) efficiency (Fv:Fm). Treatment of stressed leaves with L-galactono-1,4-lactone (GL) increased their ascorbic acid content and enhanced photochemical and non-photochemical quenching of chlorophyll fluorescence. GL reduced oxidative damage to photosynthetic proteins of droughted plants, but it reverted the decrease in electron transport activity and PSII efficiency only partially, suggesting that other factors also contributed to loss of photosystem activity in droughted plants. Increasing the ascorbic acid content of leaves might be an effective strategy to protect thylakoid membranes fromoxidative damage in water-stressed leaves.