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Changes in thiol status of rice (Oryza sativa L.) seed during development and storage
Summary
Seed development and storage could be thought as a dehydrate condition and aging process , respectively. Dehydration and aging are frequently thought to involve oxidative damage that could be prevented or counteracted by antioxidant substrates. It is well known that non-protein sulfhydryl compounds (thiol) are essential in cellular functioning but also sensitive to oxidative stress in general. In order to elucidate what role do such thiol compounds changes play in seed development and storage. We therefore investigate the thiol content and it*s redox state in different seed development and storage stages. In rice seeds, total glutathione and oxidized glutathione showed a marked increase but reduced glutathione decrease in caryopsis and embryo during seed development. Bound form glutathione, total thiol content, free thiol content and disulfide maintain in same levels during seed development. Analysis of glutathione redox in seed at various stages on development indicated that high percentage( 70-80 %) of glutathione is in oxidized form. Matured rice seeds contained the highest concentrations of glutathione and largely maintained in its oxidized form, which is an indication of oxidative stress. Embryo is a major sink for the accumulation thiol compounds during seed development. Analyses of germination, thiol compounds in seed under different storage conditions indicated that total glutathione, reduced glutathione, bound form glutathione and total thiol content in caryopsis and embryo were decreased linearly at ambient condition. Levels of oxidized glutathione increased before six months storage but decreased later. These results also reflected oxidative stress under storage condition. Seeds stored at 10℃condition could relief the degree of glutathione oxidation. Although data showed that the viability of rice seed was not directly related to the redox status of thiol compounds, but changes of glutathione status might be a good indicator of seed quality during storage.
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