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Light modulated activity of root alkaline/neutral invertase involves the interaction with 14‐3‐3 proteins
Author(s) -
Gao Jing,
Kleeff Paula J. M.,
Oecking Claudia,
Li Ka Wan,
Erban Alexander,
Kopka Joachim,
Hincha Dirk K.,
Boer Albertus H.
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12677
Subject(s) - invertase , biochemistry , mutant , fructose , phosphorylation , cytosol , chemistry , signal transduction , protein kinase a , biology , enzyme , microbiology and biotechnology , gene
Summary Alkaline/neutral invertases ( A / N ‐Invs) are now recognized as essential proteins in plant life. They catalyze the irreversible breakdown of sucrose into glucose and fructose and thus supply the cells with energy as well as signaling molecules. In this study we report on a mechanism that affects the activity of the cytosolic invertase A t CINV 1 ( A t‐ A / N ‐ I nv G or AT 1 G 35580). We demonstrate that S er547 at the extreme C ‐terminus of the A t CINV 1 protein is a substrate of calcium‐dependent kinases ( CPK 3 and 21) and that phosphorylation creates a high‐affinity binding site for 14‐3‐3 proteins. The invertase as such has basal activity, but we provide evidence that interaction with 14‐3‐3 proteins enhances its activity. The analysis of three quadruple 14‐3‐3 mutants generated from six T ‐ DNA insertion mutants of the non‐epsilon family shows both specificity as well as redundancy for this function of 14‐3‐3 proteins. The strong reduction in hexose levels in the roots of one 14‐3‐3 quadruple mutant plant is in line with the activating function of 14‐3‐3 proteins. The physiological relevance of this mechanism that affects A / N ‐invertase activity is underscored by the light‐induced activation and is another example of the central role of 14‐3‐3 proteins in mediating dark/light signaling. The nature of the light‐induced signal that travels from the shoot to root and the question whether this signal is transmitted via cytosolic C a ++ changes that activate calcium‐dependent kinases, await further study.