Down-regulation of catalase activity contributes to senescence induction in wheat leaves exposed to shading stress.

CAUSIN, H. F.; MARCHETTI, C. F.; PENA, L. B.; GALLEGO, S. M.; BARNEIX, A. J.

BIOLOGIA PLANTARUM

SPRINGER

Lugar: Berlin; Año: 2015 vol. 59 p. 154 - 162

0006-3134

In  shaded wheat  (Triticum  aestivum L.) leaves,  the  suppression of  blue  radiation (BR)  triggers  senescence. This  phenomenon is correlated toan increase in oxidative stress symptoms and a decrease of catalase (CAT)activity, among other traits. Previous data suggest that the radiation signaltransduction pathway may involve changes in Ca2+ and H2O2 homeostasis. Forbetter a understanding of the interaction among the spectral composition ofradiation, Ca2+ availability, and the antioxidant metabolismin the regulation of shade-induced senescence, detached wheat leaves wereplaced in a growth  chamber  and exposed  to  either blue  (B,  high BR  transmittance)  and/or green  (G,  very low  BR  transmittance) Lee ® filters in the absenceor presence of 0.8 mM verapamil (a Ca2+  channels blocker), 4.0 mM EGTA (a Ca2+ chelator),or 8.0 mM 3-amino-1,2,4-triazole (a CAT inhibitor). At defined time points, theleaf samples were analyzed for changes in chlorophyll  content,  specific activities  of  CAT, ascorbate  peroxidase  (APX),   and guaiacol  peroxidase  (POX), CAT isozymes, and gene expression of CAT1, CAT2, and two senescencemarkers (TaSAG1 and TaSAG3). BR transmittance decreased the chlorophyll degradation rate and SAG genesexpression either in leaves  continuouslyexposed under the B filter, as well as in leavespreviously exposed under the G filter. The effect of BR was associated with the maintenanceof   a  high   CAT   (but  not   APX   and  POX)   activity,   and  it   was   suppressed  either   in   the  presence   of 3-AT or when Ca2+ availability wasdecreased. BR altered the CAT activity both at the transcriptional and at thepost-transcriptional level. Nevertheless, different responses of CAT isozymesand CAT genes expression profiles to specific treatment combinationsindicate that they differed in their regulatory pathways.