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Evidence for a slow-turnover form of the Ca2+-independent phosphoenolpyruvate carboxylase kinase in the aleurone-endosperm tissue of germinating barley seeds
MedLine Citation:
PMID:  9952447     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Phosphoenolpyruvate carboxylase (PEPC) activity was detected in aleurone-endosperm extracts of barley (Hordeum vulgare) seeds during germination, and specific anti-sorghum (Sorghum bicolor) C4 PEPC polyclonal antibodies immunodecorated constitutive 103-kD and inducible 108-kD PEPC polypeptides in western analysis. The 103- and 108-kD polypeptides were radiolabeled in situ after imbibition for up to 1.5 d in 32P-labeled inorganic phosphate. In vitro phosphorylation by a Ca2+-independent PEPC protein kinase (PK) in crude extracts enhanced the enzyme's velocity and decreased its sensitivity to L-malate at suboptimal pH and [PEP]. Isolated aleurone cell protoplasts contained both phosphorylated PEPC and a Ca2+-independent PEPC-PK that was partially purified by affinity chromatography on blue dextran-agarose. This PK activity was present in dry seeds, and PEPC phosphorylation in situ during imbibition was not affected by the cytosolic protein-synthesis inhibitor cycloheximide, by weak acids, or by various pharmacological reagents that had proven to be effective blockers of the light signal transduction chain and PEPC phosphorylation in C4 mesophyll protoplasts. These collective data support the hypothesis that this Ca2+-independent PEPC-PK was formed during maturation of barley seeds and that its presumed underlying signaling elements were no longer operative during germination.
Authors:
Osuna; Pierre; Gonzalez; Alvarez; Cejudo; Echevarria; Vidal
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Publication Detail:
Type:  JOURNAL ARTICLE    
Journal Detail:
Title:  Plant physiology     Volume:  119     ISSN:  1532-2548     ISO Abbreviation:  Plant Physiol.     Publication Date:  1999 Feb 
Date Detail:
Created Date:  1999-02-24     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  -    
Other Details:
Languages:  Eng     Pagination:  511-20     Citation Subset:  -    
Affiliation:
Departamento de Biologia Vegetal, Facultad de Biologia, Universidad de Sevilla, Avenida Reina Mercedes no. 6, 41012 Sevilla, Spain (L.O., R.A., C.E.).
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