Journal Article

Three Types of Tobacco Calmodulins Characteristically Activate Plant NAD Kinase at Different Ca<sup>2+</sup> Concentrations and pHs

Eri Karita, Hiromoto Yamakawa, Ichiro Mitsuhara, Kazuyuki Kuchitsu and Yuko Ohashi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 10, pages 1371-1379
Published in print October 2004 | ISSN: 0032-0781
Published online October 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch158
Three Types of Tobacco Calmodulins Characteristically Activate Plant NAD Kinase at Different Ca2+ Concentrations and pHs

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  • Molecular and Cell Biology
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We previously reported that three types of tobacco calmodulin (CaM) isoforms originated from 13 genes are differently regulated at the transcript and protein levels in response to wounding and tobacco mosaic virus-induced hypersensitive reaction (HR); wound-inducible type I and HR-inducible type III levels increased after wounding and HR, respectively, while type II, whose expression is constitutive and wound responsible, remained unchanged. Here, we show that these CaMs differentially activate target enzymes; rat NO synthase was activated most effectively by type III, moderately by type I and weakly by type II, and plant NAD kinase (NADK) was activated in the inverse order. Furthermore, we found that a suitable Ca2+ concentration differs by type; type II activated NADK at lower Ca2+ of around 0.1 µM, which is the cytosolic concentration in unstimulated cells, type I did so at 1–5 µM, which is the increased Ca2+ concentration in stimulated cells, while type III did not at any Ca2+ level. NADK activation was highest over a pH range of 7.1–6.8 for which the cytosolic pH reportedly changed from 7.5 after being stimulated. Thus, tobacco CaMs, especially type I, effectively activate NADK in stimuli-induced conditions.

Keywords: Keywords: Calmodulin — Calcium — NAD kinase — NO synthase — Tobacco.; Abbreviations: CaM, calmodulin; [Ca2+]cyt, cytosolic Ca2+ concentration; CaN, calcineurin; HR, hypersensitive reaction; NADK, NAD+ kinase; NO, nitric oxide; NOS, nitric oxide synthase; PR, pathogenesis-related; ROS, reactive oxygen species; TMV, tobacco mosaic virus.

Journal Article.  6044 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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