Regulation of starch accumulation by granule-associated plant 14-3-3 proteins
In higher plants the production of starch is orchestrated by chloroplast-localized biosynthetic enzymes, namely starch synthases, ADP-glucose pyrophosphorylase, and starch branching and debranching enzymes. Diurnal regulation of these enzymes, as well as starch-degrading enzymes, influences both the...
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Published in | Proceedings of the National Academy of Sciences - PNAS Vol. 98; no. 2; pp. 765 - 770 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
16.01.2001
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Online Access | Get full text |
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Summary: | In higher plants the production of starch is orchestrated by
chloroplast-localized biosynthetic enzymes, namely starch synthases,
ADP-glucose pyrophosphorylase, and starch branching and debranching
enzymes. Diurnal regulation of these enzymes, as well as
starch-degrading enzymes, influences both the levels and composition of
starch, and is dependent in some instances upon phosphorylation-linked
regulation. The phosphoserine/threonine-binding 14-3-3 proteins
participate in environmentally responsive phosphorylation-related
regulatory functions in plants, and as such are potentially involved in
starch regulation. We report here that reduction of the ɛ subgroup of
Arabidopsis
14-3-3 proteins by antisense technology
resulted in a 2- to 4-fold increase in leaf starch accumulation.
Dark-governed starch breakdown was unaffected in these “antisense
plants,” indicating an unaltered starch-degradation pathway and
suggesting a role for 14-3-3 proteins in regulation of starch
synthesis. Absorption spectra and gelatinization properties indicate
that the starch from the antisense plants has an altered branched
glucan composition. Biochemical characterization of protease-treated
starch granules from both
Arabidopsis
leaves and maize
endosperm showed that 14-3-3 proteins are internal intrinsic granule
proteins. These data suggest a direct role for 14-3-3 proteins in
starch accumulation. The starch synthase III family is a possible
target for 14-3-3 protein regulation because, uniquely among
plastid-localized starch metabolic enzymes, all members of the family
contain the conserved 14-3-3 protein
phosphoserine/threonine-binding consensus motif. This
possibility is strengthened by immunocapture using antibodies to DU1, a
maize starch synthase III family member, and direct interaction with
biotinylated 14-3-3 protein, both of which demonstrated an
association between 14-3-3 proteins and DU1 or DU1-like proteins. |
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ISSN: | 0027-8424 1091-6490 |
DOI: | 10.1073/pnas.98.2.765 |