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Calreticulin expression in plant cells: developmental regulation, tissue specificity and intracellular distribution

Calreticulin expression in plant cells: developmental regulation, tissue specificity and... The tissue-specific expression pattern and the intracellular distribution of the Ca2+-binding protein calreticulin at the mRNA and protein levels have been studied during somatic and zygotic embryogenesis of Nicotiana plumbaginifolia Viv. A full-length cDNA sequence encoding calreticulin was isolated from a λ Zap cDNA library from early developmental stages of somatic embryogenesis. The deduced amino acid sequence of the calreticulin from N. plumbaginifolia shows high homology to the corresponding proteins of tobacco (98.2% identity), maize (80%) and barley (76.5%), and more than 55% homology to animal calreticulins, and the sequence motifs with established functions found in calreticulins of other species were quite conserved. Northern experiments revealed a developmental regulation of the calreticulin transcript with a maximum during the early stages of somatic embryogenesis and an auxin dependence during in-vitro cell culture. α-Naphthaleneacetic acid stimulated calreticulin expression whereas 2,4-dichlorophenoxyacetic acid reduced it. Immunohistological analysis of calreticulin distribution in the ovaries during zygotic embryogenesis showed that calreticulin biosynthesis started tissue specifically, with a high abundance in the endothelium of the integument in the ovules, followed by calreticulin accumulation in the embryo proper and in the associated endosperm at the late globular stage of embryogenesis. Using immunogold labeling, calreticulin was intracellularly localized with a high abundance to the Golgi compartment and to patches on the surface of dividing protoplasts. Smaller amounts were found in the endoplasmic reticulum and plasma membranes. The functional role of calreticulin in posttranslational processing and translocation processes, apart from its postulated function in cellular Ca2+ homeostasis, is discussed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Planta Springer Journals

Calreticulin expression in plant cells: developmental regulation, tissue specificity and intracellular distribution

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References (29)

Publisher
Springer Journals
Copyright
Copyright © 1998 by Springer-Verlag Berlin Heidelberg
Subject
Life Sciences; Plant Sciences; Agriculture; Ecology; Forestry
ISSN
0032-0935
eISSN
1432-2048
DOI
10.1007/s004250050427
pmid
9821685
Publisher site
See Article on Publisher Site

Abstract

The tissue-specific expression pattern and the intracellular distribution of the Ca2+-binding protein calreticulin at the mRNA and protein levels have been studied during somatic and zygotic embryogenesis of Nicotiana plumbaginifolia Viv. A full-length cDNA sequence encoding calreticulin was isolated from a λ Zap cDNA library from early developmental stages of somatic embryogenesis. The deduced amino acid sequence of the calreticulin from N. plumbaginifolia shows high homology to the corresponding proteins of tobacco (98.2% identity), maize (80%) and barley (76.5%), and more than 55% homology to animal calreticulins, and the sequence motifs with established functions found in calreticulins of other species were quite conserved. Northern experiments revealed a developmental regulation of the calreticulin transcript with a maximum during the early stages of somatic embryogenesis and an auxin dependence during in-vitro cell culture. α-Naphthaleneacetic acid stimulated calreticulin expression whereas 2,4-dichlorophenoxyacetic acid reduced it. Immunohistological analysis of calreticulin distribution in the ovaries during zygotic embryogenesis showed that calreticulin biosynthesis started tissue specifically, with a high abundance in the endothelium of the integument in the ovules, followed by calreticulin accumulation in the embryo proper and in the associated endosperm at the late globular stage of embryogenesis. Using immunogold labeling, calreticulin was intracellularly localized with a high abundance to the Golgi compartment and to patches on the surface of dividing protoplasts. Smaller amounts were found in the endoplasmic reticulum and plasma membranes. The functional role of calreticulin in posttranslational processing and translocation processes, apart from its postulated function in cellular Ca2+ homeostasis, is discussed.

Journal

PlantaSpringer Journals

Published: Oct 7, 1998

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