The plant mitochondrial electron transport chain influences
carbon and
nitrogen metabolism under near anoxic conditions through its involvement in the phytoglobin-
nitric oxide cycle, where the respiratory chain reduces
nitrite to
nitric oxide (NO), followed by NO conversion to
nitrate by class 1 phytoglobin. Wild type (WT) and transgenic tobacco (Nicotiana tabacum L.) with differing amounts of
alternative oxidase (AOX) were used to manipulate NO generation under
hypoxia, and to examine whether this in turn influenced the gene expression of two stress-related
amino acid biosynthetic pathways, the plastid-localized phosphorylated pathway of
serine biosynthesis (
PPSB), and the γ-
aminobutyric acid (
GABA) shunt. Under
hypoxia, leaf NO emission rate was highest in AOX overexpressors and lowest in AOX knockdowns, with WT showing an intermediate rate. In turn, the rate of NO emission correlated with the degree to which
amino acids accumulated. This
amino acid accumulation was associated with the increased expression of the
enzymes of the stress-related
amino acid biosynthetic pathways. However, induction of the
PPSB occurred much earlier than the
GABA shunt. This work shows that high rates of NO turnover associate with rapid gene induction of the
PPSB, establishing a clear link between this pathway and the maintenance of
carbon,
nitrogen and energy metabolism under
hypoxia.