Journal Article

Control of the Synthesis and Subcellular Targeting of the Two <i>GDH</i> Genes Products in Leaves and Stems of <i>Nicotiana plumbaginifolia</i> and <i>Arabidopsis thaliana</i>

Jean-Xavier Fontaine, Francesca Saladino, Caterina Agrimonti, Magali Bedu, Thérèse Tercé-Laforgue, Thierry Tétu, Bertrand Hirel, Francesco M. Restivo and Frédéric Dubois

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 47, issue 3, pages 410-418
Published in print March 2006 | ISSN: 0032-0781
Published online March 2006 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcj008
Control of the Synthesis and Subcellular Targeting of the Two GDH Genes Products in Leaves and Stems of Nicotiana plumbaginifolia and Arabidopsis thaliana

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Although the physiological role of the enzyme glutamate dehydrogenase which catalyses in vitro the reversible amination of 2-oxoglutarate to glutamate remains to be elucidated, it is now well established that in higher plants the enzyme preferentially occurs in the mitochondria of phloem companion cells. The Nicotiana plumbaginifolia and Arabidopis thaliana enzyme is encoded by two distinct genes encoding either an α- or a β-subunit. Using antisense plants and mutants impaired in the expression of either of the two genes, we showed that in leaves and stems both the α- and β-subunits are targeted to the mitochondria of the companion cells. In addition, we found in both species that there is a compensatory mechanism up-regulating the expression of the α-subunit in the stems when the expression of the β-subunit is impaired in the leaves, and of the β-subunit in the leaves when the expression of the α-subunit is impaired in the stems. When one of the two genes encoding glutamate dehydrogenase is ectopically expressed, the corresponding protein is targeted to the mitochondria of both leaf and stem parenchyma cells and its production is increased in the companion cells. These results are discussed in relation to the possible signalling and/or physiological function of the enzyme which appears to be coordinated in leaves and stems.

Keywords: Companion cells; Glutamate dehydrogenase; Leaves; Mitochondria; Stems; Subcellular targeting; BSA, bovine serum albumin; CaMV, cauliflower mosaic virus; C, carbon; CC, companion cell; GDH, glutamate dehydrogenase; N, nitrogen; WT, wild type

Journal Article.  6363 words.  Illustrated.

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

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