Abstract
A distribution of N to mitochondrial proteins increases under low-N conditions. The alternative oxidase (AOX), which is unique in higher plants, is one of the electron transport chain (ETC) components induced under the low-N conditions. Since AOX is uncoupled to ATP production, this enzyme is wasteful with NAD(P)H. However, AOX can dissipate the excess NAD(P)H without being limited by proton gradient. In the aox anti-sense cells grown under the low-N condition, the C/N ratio were higher than those of WT. This indicates that AOX functions as a C/N balancer by consuming the excess sugars. Recent studies have reported that, under the ammonium or nitrate as an N source, the expression and maximal activity of AOX were increased or decreased, respectively. We revealed that AOX1a could function, and be regulated by cellular N compounds. We will discuss regulations of the C/N ratio by AOX and other plant-characteristic components of ETC.
