title: Light modulated activity of root alkaline/neutral invertase involves the interaction with 14-3-3 proteins.
abstract: 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 AtCINV1 (At-A/N-InvG or AT1G35580). We demonstrate that Ser547 at the extreme C-terminus of the AtCINV1 protein is a substrate of calcium-dependent kinases (CPK3 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 Ca(++) changes that activate calcium-dependent kinases, await further study.
authors.affiliation: Department of Structural Biology, Faculty of Earth and Life Sciences, Vrije Universiteit, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands.
authors.forename: Jing
authors.initials: J
authors.lastname: Gao
authors.forename: Paula J M
authors.initials: PJ
authors.lastname: van Kleeff
authors.forename: Claudia
authors.initials: C
authors.lastname: Oecking
authors.forename: Ka Wan
authors.initials: KW
authors.lastname: Li
authors.forename: Alexander
authors.initials: A
authors.lastname: Erban
authors.forename: Joachim
authors.initials: J
authors.lastname: Kopka
authors.forename: Dirk K
authors.initials: DK
authors.lastname: Hincha
authors.forename: Albertus H
authors.initials: AH
authors.lastname: de Boer
mesh_terms: D048948:14-3-3 Proteins / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial; D005632:Fructose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D008027:Light; D009154:Mutation; D010766:Phosphorylation; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D043324:beta-Fructofuranosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; C036483:T-DNA; D005632:Fructose; D012694:Serine; D011494:Protein Kinases; C583356:At4g04720 protein, Arabidopsis; C516786:CPK3 protein, Arabidopsis; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C000607060:CINV1 protein, Arabidopsis; D043324:beta-Fructofuranosidase; D005947:Glucose
keywords: 14-3-3; Arabidopsis thaliana; alkaline/neutral invertase; calcium-dependent protein kinases; dark/light; sucrose