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α-amylase is not required for breakdown of transitory starch in Arabidopsis leaves
journal contribution
posted on 2023-05-18, 11:22 authored by Yu, T-S, Zeeman, SC, Thorneycroft, D, Fulton, DC, Dunstan, H, Lue, W-L, Hegemann, B, Tung, S-Y, Umemoto, T, Chapple, A, Tsai, D-L, Wang, S-M, Smith, AM, Chen, J, Steven SmithSteven SmithThe Arabidopsis thaliana genome encodes three α-amylase-like proteins (AtAMY1, AtAMY2, and AtAMY3). Only AtAMY3 has a predicted N-terminal transit peptide for plastidial localization. AtAMY3 is an unusually large α-amylase (93.5 kDa) with the C-terminal half showing similarity to other known α-amylases. When expressed in Escherichia coli, both the whole AtAMY3 protein and the C-terminal half alone show α-amylase activity. We show that AtAMY3 is localized in chloroplasts. The starch-excess mutant of Arabidopsis sex4, previously shown to have reduced plastidial α-amylase activity, is deficient in AtAMY3 protein. Unexpectedly, T-DNA knock-out mutants of AtAMY3 have the same diurnal pattern of transitory starch metabolism as the wild type. These results show that AtAMY3 is not required for transitory starch breakdown and that the starch-excess phenotype of the sex4 mutant is not caused simply by deficiency of AtAMY3 protein. Knock-out mutants in the predicted non-plastidial α-amylases AtAMY1 and AtAMY2 were also isolated, and these displayed normal starch breakdown in the dark as expected for extraplastidial amylases. Furthermore, all three AtAMY double knock-out mutant combinations and the triple knock-out degraded their leaf starch normally. We conclude that α-amylase is not necessary for transitory starch breakdown in Arabidopsis leaves.
History
Publication title
Journal of Biological ChemistryVolume
280Issue
11Pagination
9773-9779ISSN
0021-9258Department/School
School of Natural SciencesPublisher
Amer Soc Biochemistry Molecular Biology IncPlace of publication
9650 Rockville Pike, Bethesda, USA, Md, 20814-3996Rights statement
© 2005 by The American Society for Biochemistry and Molecular BiologyRepository Status
- Restricted