Effect of short- and long-term phosphate stress on the non-phosphorylating pathway of mitochondrial electron transport in Arabidopsis thaliana

Wild-type Arabidopsis thaliana L. seedlings generated in liquid culture were subjected to long- and short-term phosphate (Pi) stress to assess the response of the non-phosphorylating pathway of mitochondrial electron transport, comprising the internal (NDin) and external (NDex) non-phosphorylating NAD(P)H dehydrogenases and the alternative oxidase (AOX). Tissue Pi levels decreased but anthocyanin levels increased in both short- and long-term Pi stress. Oxidative damage was either lower or unchanged in response to short- and long-term Pi term stress. NDin and AOX capacity were elevated only in response to long-term Pi stress whereas NDex capacity was elevated only in response to short-term Pi stress. The only ND genes with elevated transcript levels in response to both short- and long-term Pi stress were Atnda2 (an NDin) and Atndb2 (an NDex). The binding site for PHR1, a transcription factor involved in the Pi stress response, was found in the promoter regions of Atnda2 and Atndb2. Results of this study indicate that a non-phosphorylating mitochondrial electron transport chain consisting of NDA2, NDB2 and AOX is synthesised to maintain respiratory electron flow through the mitochondrial electron transport chain during Pi stress.