Molecular and physiological study of magnesium-dependent soluble inorganic pyrophosphatases in Solanum tuberosum L. | Etude moleculaire et physiologique de pyrophosphatases inorganiques solubles dependantes de magnesium chez Solanum tuberosum L.
1997
Rojas-Beltram, J.A.
Magnesium dependent soluble inorganic pyrophosphatases (PPases, EC 3.6.1.1) were studied in potato (Solanum tuberosum L. ssp. tuberosum), in order to precise their role in the metabolism, mainly in carbon metabolism. Three distinct cDNAs corresponding to PPases were cloned and characterized. From a nucleotide sequence point of view, two of them are very similar to the clone used for raising the polyclonal antibodies (99.8 per cent and 99.0 per cent of identity, ppast-1), whereas the third one proves to be different (72.4 per cent of identity, ppast-2). Chromosomal mapping analyses identified two loci corresponding to ppast-1 and one locus corresponding to ppast-2 in the potato haploid genome. The expression products of ppast-1 and ppast-2 are regulated during development and probably localized in the cytosol. Moreover, the expression product of ppast-1 shows remarkable biochemical differences when compared to the major (chloroplastic) PPase activity and, from a phylogenetic and structural point of view, ppast-1 and ppast-2 are more closely related to prokaryotic than to eukaryotic PPases. Based on these observations and on the results of the phenotypic and histological studies of transgenic clones inhibited in the expression of ppast-1 by the antisense RNA technology, the likely physiological function of these PPases is discussed
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