METABOLIC REPROGRAMMING DURING LEAF SENESCENCE IS AFFECTED BY CHLOROPLAST REDOX STATE

MAYTA MARTÍN; CARRILLO NÉSTOR; LODEYRO A; HAJIREZAEI M-R

Rosario

Simposio; Second Latin American Metabolic Profiling Symposium; 2016

IBR

METABOLIC REPROGRAMMING DURING LEAFSENESCENCE IS AFFECTED BY CHLOROPLAST REDOX STATE Mayta ML1, Hajirezaei, MR2,Lodeyro, A1, Carrillo, N11Institute of Molecular and Cellular Biology of Rosario (IBR-CONICET),Rosario, Argentina. e-mail:mayta@ibr-conicet.gov.ar2Leibniz Institute for Plant Genetics and Crop Research(IPK), Gatersleben, Germany.Keywords: Senescence,Chloroplast, Reactive oxygen species, Flavodoxin, Metabolite profillingSenescence represents the finalstage of leaf development. It is a geneticallyprogrammed sequence of biochemical and physiological changes that comprisechloroplast dismantling and degradation of macromolecules such as proteins,nucleic acids and lipids (1) in order to mobilize nutrients from senescing leaves to otherparts of the plant, such as younger leaves, developing seeds or storagetissues. Hence, it is vital for plant survival and reproduction. The primary physiological purpose is the recycling of N-containingcompounds(e.g. amino acids) and sugars, which mainly derive fromchloroplasts (2). Therefore, senescence involves substantial metabolicreprogramming, and metaboliteprofiling analysis has been used to characterize plants with delayed senescence(3). Transgenic tobacco plants expressing the electron carrier proteinflavodoxin (Fld) from Anabaena in their chloroplasts (pfld plants) display a ?stay-green? phenotype in leaves andlower reactive oxygen species accumulation in the organelle during leafsenescence. Under environmental stress conditions, Fld has been shown topreserve central metabolic pathways presumably by acting as an electron donorfor critical reactions in the chloroplast (4, 5). To evaluate if a similar roleis played during senescence we determined the presence and quantity of severalamino acids, soluble sugars, starch and phosphorylated metabolites involvedin primary processes in young and senescent leaves fromwild-type and transgenic lines. Fld expression in chlororplasts was able todelay the inhibition of central metabolic routes in senescent leaves, asreflected by higher levels of key aminoacids and phosphorylated sugars. Sucroselevels were also higher and starch and monosaccharides were lower in pfld plants. Additionally, several formsof citokinins (CKs) and auxins (two important senescence-related phytohormones)were measured. No differences were observed for auxins in old leaves of alllines. Instead, transgenic pfld linesdisplayed higher levels of a major active CKs form and lower levels of a majorCKs reserve form. Taken together, the results indicate that signals respondingto chloroplast redox state modulate the progress of metabolic changes duringleaf senescence.  REFERENCESSedigheh, H. G. y col. BMC Res. Notes, 2011, 4, 477.Carrión, C. A. y col.Exp Bot. 2013, 64, 4967?4980.Merewitz, E. B. y col. J Exp Bot., 2012, 63, 1315-1328.Tognetti, V. B. y col. Proc. Natl Acad. Sci. USA, 2007, 104, 11495-11500.Zurbriggen, M. D. y col. Plant J., 2009, 60, 962-973. ACKNOWLEDGEMENTSNATIONAL RESEARCH COUNCIL (CONICET),NATIONAL RESEARCH AGENCY (ANCYPT), NATIONAL UNIVERSITY OF ROSARIO (UNR), EUROPEANMOLECULAR BIOLOGY ORGANIZATION (EMBO)