Repression of formate dehydrogenase in Solanum tuberosum increases steady-state levels of formate and accelerates the accumulation of proline in response to osmotic stress.
Formate dehydrogenase (FDH, EC 1.2.1.2.) is a soluble mitochondrial enzyme capable of oxidizing formate into CO2 in the presence of NAD+. It is abundant in non-green tissues and scarce in photosynthetic tissues. Under stress, FDH transcripts (and protein) accumulate in leaves, and leaf mitochondria acquire the ability to use formate as a respiratory substrate. In this paper, we describe the analysis of transgenic potato plants under-expressing FDH, obtained in order to understand the physiological function of FDH. Plants expressing low FDH activities were selected and the study was focused on a line (AS23) showing no detectable FDH activity. AS23 plants were morphologically indistinguishable from control plants, and grew normally under standard conditions. However, mitochondria isolated from AS23 tubers could not use formate as a respiratory substrate. Steady-state levels of formate were higher in AS23 leaves and tubers than in control plants. Tubers of untransformed plants oxidized 14C formate into 14CO2 but AS23 tubers accumulated it. In order to reveal a possible phenotype under stress conditions, control and AS23 plants were submitted to drought and cold. These treatments dramatically induced FDH transcripts in control plants but, whatever the growth conditions, no 1.4 kb FDH transcripts were detected in leaves of AS23 plants. Amongst various biochemical and molecular differences between stressed AS23 and control plants, the most striking was a dramatically faster accumulation of proline in the leaves of drought-stressed plants under-expressing FDH.
Ambard-Bretteville
Françoise
F
Institut de Biotechnologie des Plantes UMR CNRS 8618, Université Paris-Sud, 91405 Orsay cedex, France.
Sorin
Céline
C
Rébeillé
Fabrice
F
Hourton-Cabassa
Cécile
C
Colas des Francs-Small
Catherine
C
D000596:Amino Acids / Q000378:metabolism; D003080:Cold Temperature; D004190:Disasters; D005557:Formaldehyde / Q000378:metabolism; D005560:Formate Dehydrogenases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D005561:Formates / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D000432:Methanol / Q000378:metabolism; D009997:Osmotic Pressure; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified; D011392:Proline / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011198:Solanum tuberosum / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
D000596:Amino Acids; D005561:Formates; D012333:RNA, Messenger; D005557:Formaldehyde; D011392:Proline; D005560:Formate Dehydrogenases; D000432:Methanol