Methionyl sulfoxide content and protein‐methionine‐S‐oxide reductase activity in response to water deficits or high temperature

Abstract

Cellular injury resulting from partially reduced oxygen species (superoxide, peroxides and/or hydroxyl radicals) or singlet oxygen frequently increases during environmental stress. Because protein methionine residues are susceptible to oxidation, we investigated the effects of water‐deficit stress and high temperature stress on the content of oxidized methionyl residues [Met(O)] in leaves. Leaf proteins from water‐deficit‐stressed cotton (Gossypium hirsutum L. cv. Paymaster HS‐26). pea (Pisum sativum L. cv. Progress No. 9). wheat (Triticum aestivum L. em. Thell. cv. Len) and potato (Solanum tuberosum L. cv. Norgold M) and from the leaves of high‐temperature‐stressed pea seedlings were evaluated. The activity of protein methionine‐S‐oxide reductase (PrMSR). an enzyme responsible for re‐reducing oxidized methionyl residues, was also determined. Protein Met(O) content did not change in response to either water‐deficit or high temperature stress. PrMSR activity decreased in pea and cotton leaves, remained unchanged in potato leaves and significantly increased in leaves of water‐deficit‐stressed wheat. The findings demonstrate that these plants have developed protection systems that effectively maintain stable levels of oxidized methionyl residues in leaf proteins despite exposure to severe water and high temperature stress. The findings also suggest that changes in PrMSR activity do not fully account for the observed maintenance of protein methionyl sulfoxide content at constant levels.