Journal Article

Activation of an ER-body-localized β-Glucosidase via a Cytosolic Binding Partner in Damaged Tissues of <i>Arabidopsis thaliana</i>

Atsushi J. Nagano, Ryo Matsushima and Ikuko Hara-Nishimura

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 7, pages 1140-1148
Published in print July 2005 | ISSN: 0032-0781
Published online July 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci126
Activation of an ER-body-localized β-Glucosidase via a Cytosolic Binding Partner in Damaged Tissues of Arabidopsis thaliana

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  • Biochemistry
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The ER body is an endoplasmic reticulum (ER)-derived organelle. Because ER bodies are induced by wounding and methyl jasmonate (MeJA) treatment in rosette leaves, they might be responsible for defense systems. Recently, we isolated nai1 mutants that have no ER body and showed that the levels of PYK10 and PBP1 (PYK10-binding protein 1: At3g16420) were decreased in nai1 mutants. PYK10 is a β-glucosidase that is localized in ER bodies. PBP1 consists of two repeated regions, each of which is highly homologous to the α-chain of jacalin, a carbohydrate-binding protein (lectin) of Artocarpus integriforia. We show in this study that PYK10 has two forms, an active form and an inactive form. The amount of active form increased during incubation of root homogenate. On the other hand, PYK10 separated into soluble and insoluble forms. Active PYK10 molecules mainly occurred as the insoluble form and inactive PYK10 molecules remain soluble. This suggests that the activation of PYK10 needs polymerization. In homogenates of both a pbp1 mutant and the wild type, PYK10 becomes insoluble, while PYK10 activity in pbp1 is only half of that in the wild type. PBP1 has an ability to interact with PYK10. Nonetheless, PBP1 does not bind active PYK10. These results suggest that PBP1 has some effect on the activation of PYK10. In addition, PBP1 was found to have a different subcellular distribution from PYK10. PBP1 may act like a molecular chaperone that facilitates the correct polymerization of PYK10, when tissues are damaged and subcellular structures are destroyed by pests.

Keywords: Arabidopsis thaliana; ER body; β-Glucosidase; Lectin; Myrosinase-binding protein; PYK10; BGAF, β-glucosidase aggregation factor; BN, blue native; CBB, Coomassie brilliant blue; DSS, disuccinimidyl suberate; GFP, green fluorescent protein; MBP, myrosinase-binding protein; MeJA, methyl jasmonate; PBP1, PYK10-binding protein 1

Journal Article.  6681 words.  Illustrated.

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

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