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PMID:17333023

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Citation

Han, SE, Seo, YS, Kim, D, Sung, SK and Kim, WT (2007) Expression of MdCAS1 and MdCAS2, encoding apple beta-cyanoalanine synthase homologs, is concomitantly induced during ripening and implicates MdCASs in the possible role of the cyanide detoxification in Fuji apple (Malus domestica Borkh.) fruits. Plant Cell Rep. 26:1321-31

Abstract

Fruit ripening involves complex biochemical and physiological changes. Ethylene is an essential hormone for the ripening of climacteric fruits. In the process of ethylene biosynthesis, cyanide (HCN), an extremely toxic compound, is produced as a co-product. Thus, most cyanide produced during fruit ripening should be detoxified rapidly by fruit cells. In higher plants, the key enzyme involved in the detoxification of HCN is beta-cyanoalanine synthase (beta-CAS). As little is known about the molecular function of beta-CAS genes in climacteric fruits, we identified two homologous genes, MdCAS1 and MdCAS2, encoding Fuji apple beta-CAS homologs. The structural features of the predicted polypeptides as well as an in vitro enzyme activity assay with bacterially expressed recombinant proteins indicated that MdCAS1 and MdCAS2 may indeed function as beta-CAS isozymes in apple fruits. RNA gel-blot studies revealed that both MdCAS1 and MdCAS2 mRNAs were coordinately induced during the ripening process of apple fruits in an expression pattern comparable with that of ACC oxidase and ethylene production. The MdCAS genes were also activated effectively by exogenous ethylene treatment and mechanical wounding. Thus, it seems like that, in ripening apple fruits, expression of MdCAS1 and MdCAS2 genes is intimately correlated with a climacteric ethylene production and ACC oxidase activity. In addition, beta-CAS enzyme activity was also enhanced as the fruit ripened, although this increase was not as dramatic as the mRNA induction pattern. Overall, these results suggest that MdCAS may play a role in cyanide detoxification in ripening apple fruits.

Links

PubMed Online version:10.1007/s00299-007-0316-9

Keywords

Amino Acid Sequence; Cyanides/metabolism; DNA, Complementary; DNA, Plant; Enzyme Induction; Fruit/enzymology; Fruit/metabolism; Gene Expression Regulation, Plant; Lyases/biosynthesis; Lyases/genetics; Lyases/metabolism; Malus/enzymology; Malus/genetics; Malus/metabolism; Molecular Sequence Data; Phylogeny

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

MALDO:CAS2

involved_in

GO:0009836: fruit ripening, climacteric

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

MALDO:CAS2

enables

GO:0050017: L-3-cyanoalanine synthase activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

MALDO:CAS1

GO:0009611: response to wounding

ECO:0000314:

P

Figure 5 (b) shows direct increase of mRNA transcript in response to mechanical wounding of the fruit with positive and negative controls.

complete
CACAO 4288

MALDO:CAS1

involved_in

GO:0009836: fruit ripening, climacteric

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

MALDO:CAS1

enables

GO:0050017: L-3-cyanoalanine synthase activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

MALDO:CAS1

involved_in

GO:0009611: response to wounding

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete


See also

References

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