Abstract
Aldehyde dehydrogenases (ALDHs) catalyze the irreversible oxidation of a wide range of reactive aldehydes to their corresponding carboxylic acids. Although the proteins have been studied from various organisms and at different growth stages, their roles in seed development have not been well elucidated. We obtained T-DNA insertional mutants in OsALDH7, which is remarkably inducible by oxidative and abiotic stresses. Interestingly, endosperms from the osaldh7 null mutants accumulated brown pigments during desiccation and storage. Extracts from the mutant seeds showed a maximum absorbance peak at 360 nm, the wavelength that melanoidin absorbs. Under UV light, those extracts also exhibited much stronger fluorescence than the wild type, suggesting that the pigments are melanoidin. These pigments started to accumulate in the late seed developmental stage, the time when OsALDH7 expression began to increase significantly. Purified OsALDH7 protein showed enzyme activities to malondialdehyde, acetaldehyde, and glyceraldehyde. These results suggest that OsALDH7 is involved in removing various aldehydes formed by oxidative stress during seed desiccation. The mutant seeds were more sensitive to our accelerated aging treatment and accumulated more malondialdehyde than the wild type. These data imply that OsALDH7 plays an important role in maintaining seed viability by detoxifying the aldehydes generated by lipid peroxidation.
Highlights
Aldehyde dehydrogenases (ALDHs) catalyze the irreversible oxidation of a wide range of reactive aldehydes to their corresponding carboxylic acids
To examine whether rice ALDH7 plays an important role in abiotic stresses, we investigated OsALDH7 expression patterns after seedlings were treated with cold, heat, drought, paraquat, Figure 4
We observed that levels of OsALDH7 transcripts started to increase at the late stage of maturation, similar to those of the late embryogenesis abundant (LEA) genes
Summary
Aldehyde dehydrogenases (ALDHs) catalyze the irreversible oxidation of a wide range of reactive aldehydes to their corresponding carboxylic acids. The mutant seeds were more sensitive to our accelerated aging treatment and accumulated more malondialdehyde than the wild type These data imply that OsALDH7 plays an important role in maintaining seed viability by detoxifying the aldehydes generated by lipid peroxidation. Lipid peroxidation and respiration result in the formation of reactive aldehydes such as malondialdehyde (MDA) and acetaldehyde, which tend to react with proteins and amino acids (Mueller, 1998; Almeras et al, 2003; Weber et al, 2004) Those reactions cause aging and seed damage (Zhang et al, 1995, 1997). ALDHs catalyze the irreversible oxidation of a wide range of reactive aldehydes to their corresponding carboxylic acids (Perozich et al, 1999; Kirch et al, 2005) They play a pivotal role in detoxifying the aldehydes generated by environmen-
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