Assimilation of
nitrate and
ammonium are vital
procedures for
plant development and
growth. From these primary paths of inorganic
nitrogen assimilation, this
metabolism integrates diverse paths for
biosynthesis of macromolecules, such as
amino acids and
nucleotides, and the central intermediate
metabolism, like
carbon metabolism and photorespiration. This
paper reports research performed in the CitEST (Citrus
Expressed Sequence Tag) database for the main
genes involved in
nitrogen metabolism and those previously described in other organisms. The results show that a complete cluster of
genes involved in the assimilation of
nitrogen and the metabolisms of
glutamine,
glutamate,
aspartate and
asparagine can be found in the CitEST data. The main
enzymes found were
nitrate reductase (NR),
nitrite reductase (NiR),
glutamine synthetase (GS),
glutamate synthetase (GOGAT),
glutamate dehydrogenase (GDH),
aspartate aminotransferase (AspAT) and
asparagine synthetase (AS). The different
enzymes involved in this
metabolism have been shown to be highly conserved among the Citrus and
Poncirus species. This
work serves as a guide for
future functional
analysis of these
enzymes in citrus.