Differential impact of amino acids on OXPHOS system activity following carbohydrate starvation in Arabidopsis cell suspensions

Abstract

Plant respiration mostly depends on the activity of glycolysis and the oxidation of organic acids in the tricarboxylic acid cycle to synthesize ATP. However, during stress situations plant cells also use amino acids as alternative substrates to donate electrons through the electron-transfer flavoprotein (ETF)/ETF:ubiquinone oxidoreductase (ETF/ETFQO) complex to the mitochondrial electron transport chain (mETC). Given this, we investigated changes of the oxidative phosphorylation (OXPHOS) system in Arabidopsis thaliana cell culture under carbohydrate starvation supplied with a range of amino acids. Induction of isovaleryl-CoA dehydrogenase (IVDH) activity was observed under carbohydrate starvation which was associated with increased amounts of IVDH protein detected by immunoblotting. Furthermore, activities of the protein complexes of the mETC were reduced under carbohydrate starvation. We also observed that OXPHOS system activity behavior is differently affected by different amino acids and that proteins associated with amino acids catabolism are upregulated in cells following carbohydrate starvation. Collectively, our results support the contention that ETF/ETFQO is an essential pathway to donate electrons to the mETC and that amino acids are alternative substrates to maintain respiration under carbohydrate starvation.

Complexome Profiling Reveals Association of PPR Proteins with Ribosomes in the Mitochondria of Plants

“…Mitochondria Isolation-preparation of organelles from Arabidopsis cell culture and leaf material was performed as described previously (31,36), except for the isolation procedure for cross-linked leaf mitochondria, which involved an additional cross-linking step. Crosslinking was performed by adding 37% [v/v] formaldehyde solution to the filtered cell homogenate to a final concentration of 0.5% [v/v].…”

An L,L-diaminopimelate aminotransferase mutation leads to metabolic shifts and growth inhibition in Arabidopsis

“…8 ). By integrating this metabolic data with the transcriptome, which displays increases of IVDH and D2HGDH , related to catabolism of BCAAs and Lys, respectively ( Engqvist et al , 2009 ; Araújo et al , 2010 ; Peng et al , 2015 ; Cavalcanti et al , 2017 ), it is reasonable to assume that alternative respiratory pathways mediated by ETF–ETFQO are up-regulated in dapat plants. Furthermore, the maintenance of similar dark respiration rates in dapat plants might also occur through oxidation of malate that is accumulated during the light period.…”

Metabolite Regulatory Interactions Control Plant Respiratory Metabolism via Target of Rapamycin (TOR) Kinase Activation

“…Gly is the predominant amino acid substrate supplied to leaf mitochondria because of photorespiration in the light. The induced use of other amino acids as respiratory substrates under carbon starvation or senescence, in particular Ile, Leu, Val, and Lys, is well studied and has been linked to a SnRK1-bZIP signal transduction pathway and the upregulation of the ETF/ETFQO complex (Araújo et al, 2010;Cavalcanti et al, 2017;Pedrotti et al, 2018). By contrast, a connection that distinguishes Ala and Pro from most other amino acids is that they are both well known to accumulate in response to certain stresses; furthermore, this accumulation occurs at least partly in the cytosol in the case of Pro (Ketchum et al, 1991;Gagneul et al, 2007).…”