1 research outputs found
Control of the Synthesis and Subcellular Targeting of the Two GDH Genes Products in Leaves and Stems of Nicotiana plumbaginifolia and Arabidopsis thaliana
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