POLYAMINES AND SODIUM NITROPRUSSIDE EXHIBITED DIFFERENT BEHAVIOUR AS PROTECTORS UNDER DARK OR Cd-INDUCED SENESCENCE

CABRERA A.; RECALDE L.; BLAGER L.; GROPPA M.D.; BENAVIDES M.P.

Congreso; LVII Reunión Anual de SAIB. Congreso Conjunto SAIB-SAMIGE 2021; 2021

POLYAMINES AND SODIUM NITROPRUSSIDE EXHIBITED DIFFERENT BEHAVIOUR AS PROTECTORS UNDER DARK OR Cd-INDUCED SENESCENCECabrera AV1; Recalde L1., Blager L1, Groppa MD1,2, Benavides MP1,2.1Departamento de Química Biológica. Facultad de Farmacia y Bioquímica. Universidad de Buenos Aires. 2IQUIFIB-CONICET. andreacab86@gmail.comPolyamines (PAs) and nitric oxide (NO) are essential for plant growth and development. It has been demonstrated that putrescine (Put), spermidine (Spd), spermine (Spm) or NO exhibit anti-senescence properties in plants. Cadmium is a metal that accelerates senescence by inducing cellular degradation. In this work, we studied how PAs or NO avoid dark or Cd-induced senescence in wheat leaves using a floating ?in vitro? model. Leaf segments were incubated in the dark with 100 µM of the three PAs or SNP (as NO donor) for 72h, or pretreated 24h with 100 µM PAs and then exposed to 50 µM Cd for 48h. Spd, Spm and SNP reduced chlorophyll degradation between 50% and 150%, but only the PAs reduced TBARS increase by 50 % compared to C during dark-induced senescence. In Cd-treated leaves, Spd and Spm partially recovered chlorophyll decay induced by Cd between 10% and 40% respectively. Electrolyte leakage (EL) was partially prevented only by Put in dark-incubated leaves, but Spd and Spm significantly reversed the 275% increase in the electrolyte leakage induced by Cd. This parameter was reduced 60% by Spd, 40% by 100 µM Spm and 65% by 25 µM Spm compared to the C. In the dark, SNP increased superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GPOX) activities, whereas Spd and Spm enhanced CAT and SOD but decreased GPOX activity respect to the C. Cd increased SOD activity 30% but reduced CAT activity more than 50% respect to the C. Exogenous added Spd recovered almost 50% of CAT activity over the values measured in Cd-treated leaves while 25 µM Spm restored the enzyme activity 30% in the presence of Cd. Histochemical detection of ROS revealed that Spd and Spm partially avoided the increase in O2.- generated by Cd but did not have any effect in preventing H2O2 formation when used alone. Cadmium increased H2O2 formation with respect to the C, and none of the PAs reversed Cd-increased H2O2 formation when used in the pretreatment assay. In the dark, only SNP reduced O2.- formation whereas H2O2 deposition was restricted by Put but enhanced by Spd and Spm.A different mode of action of PAs or NO in dark or Cd-induced senescence is suggested by these results. In the dark, the main way of action of the three PAs seemed to be through their antioxidant or scavenger properties, protecting the tissues from chlorophyll loss or avoiding lipid peroxidation, by increasing SOD and CAT activity. Under Cd exposure, Spd and Spm recovered chlorophyll loss and maintained membrane stability by reducing electrolyte leakage, but could not avoid lipid peroxidation, despite the increase in CAT or GPOX activities. SNP increased the antioxidant enzymes but could not avoid damage to tissues either avoiding electrolyte leakage or lipid peroxidation, though protected against chlorophyll degradation. Other senescence parameters are currently being evaluated to shed light on the mechanisms involved in PAs or NO action.