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Zea mays Annexins Modulate Cytosolic Free Ca2+ and Generate a Ca2+-Permeable Conductance

Laohavisit, Anuphon and Mortimer, Jennifer C and Demidchik, Vadim and Coxon, K M and Stancombe, MA and Macpherson, N and Brownlee, Colin and Hofmann, A and Webb, A A R and Miedema, Henk and Battey, N H and Davies, Julia M (2009) 'Zea mays Annexins Modulate Cytosolic Free Ca2+ and Generate a Ca2+-Permeable Conductance.' The Plant Cell, 21 (2). pp. 479-493. ISSN 1040-4651

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Abstract

Regulation of reactive oxygen species and cytosolic free calcium ([Ca2+]cyt) is central to plant function. Annexins are small proteins capable of Ca2+-dependent membrane binding or membrane insertion. They possess structural motifs that could support both peroxidase activity and calcium transport. Here, a Zea mays annexin preparation caused increases in [Ca2+]cyt when added to protoplasts of Arabidopsis thaliana roots expressing aequorin. The pharmacological profile was consistent with annexin activation (at the extracellular plasma membrane face) of Arabidopsis Ca2+-permeable nonselective cation channels. Secreted annexins could therefore modulate Ca2+ influx. As maize annexins occur in the cytosol and plasma membrane, they were incorporated at the intracellular face of lipid bilayers designed to mimic the plasma membrane. Here, they generated an instantaneously activating Ca2+-permeable conductance at mildly acidic pH that was sensitive to verapamil and Gd3+ and had a Ca2+-to-K+ permeability ratio of 0.36. These results suggest that cytosolic annexins create a Ca2+ influx pathway directly, particularly during stress responses involving acidosis. A maize annexin preparation also demonstrated in vitro peroxidase activity that appeared independent of heme association. In conclusion, this study has demonstrated that plant annexins create Ca2+-permeable transport pathways, regulate [Ca2+]cyt, and may function as peroxidases in vitro.

Item Type: Article
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health > Biological Sciences, School of
Depositing User: Jim Jamieson
Date Deposited: 11 Oct 2011 15:46
Last Modified: 14 Dec 2011 12:12
URI: http://repository.essex.ac.uk/id/eprint/1080

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