TY - JOUR
T1 - Cytokinin promotes catalase and ascorbate peroxidase activities and preserves the chloroplast integrity during dark-senescence
AU - Zavaleta-Mancera, Hilda Araceli
AU - López-Delgado, Humberto
AU - Loza-Tavera, Herminia
AU - Mora-Herrera, Martha
AU - Trevilla-Garcia, Claudia
AU - Vargas-Suárez, Martin
AU - Ougham, Helen J.
N1 - Zavaleta-Mancera, H. A., Lopez-Delgado, H., Loza-Tavera, H., Mora-Herrera, M., Trevilla-Garcia, C., Vargas-Suarez, M., Ougham, H. J. (2007). Cytokinin promotes catalase and ascorbate peroxidase activities and preserves the chloroplast integrity during dark-senescence. Journal of Plant Physiology, 164, (12), 1572-1582.
Sponsorship: Mexican Council of Science and Technology, CONACYT (grant 43866/A-1); BBSRC
PY - 2007/12/3
Y1 - 2007/12/3
N2 - Increased oxidative stress displayed during dark-senescence of wheat leaves (Triticum aestivum L.) is caused not only by the increased levels of radicals but also by a loss of antioxidant capacity. Mature leaves were incubated in 6-benzylaminopurine (BAP 10−4 M) or water (control) during 6 d in the dark. The senescence-delaying effect of BAP was associated with the retention of the chloroplast structure, 60% of the initial content of chlorophyll (Chl) and 77% of the initial content of protein. BAP reduced the degradation of the light-harvesting chlorophyll a/b binding protein (LHCP-2), and the large (LSU) and small subunits (SSU) of Rubisco. Our results indicated that the presence of the NADPH:protochlorophyllide oxidoreductase (POR, EC.1.6.99.1) was not promoted by the cytokinin, leading to the conclusion that BAP maintains the level of Chl, preventing its degradation, rather than inducing Chl biosynthesis. The internal structure of chloroplasts was maintained in BAP-treated leaves for up to 6 d, with well-organized grana thylakoids and small plastoglobuli; in contrast, chloroplasts of control leaves deteriorated rapidly from day 4 with disorganized internal membranes, and more and larger plastoglobuli. BAP increased the activities of catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) and reduced the level of H2O2 in the delayed-senescence tissue. The present research indicates that BAP reduces levels of reactive oxygen species (ROS), and enhances the activity of antioxidant enzymes (CAT, APX). Our results suggest that BAP protects the cell membranes and the photosynthetic machinery from oxidative damage during delay of senescence in the dark.
AB - Increased oxidative stress displayed during dark-senescence of wheat leaves (Triticum aestivum L.) is caused not only by the increased levels of radicals but also by a loss of antioxidant capacity. Mature leaves were incubated in 6-benzylaminopurine (BAP 10−4 M) or water (control) during 6 d in the dark. The senescence-delaying effect of BAP was associated with the retention of the chloroplast structure, 60% of the initial content of chlorophyll (Chl) and 77% of the initial content of protein. BAP reduced the degradation of the light-harvesting chlorophyll a/b binding protein (LHCP-2), and the large (LSU) and small subunits (SSU) of Rubisco. Our results indicated that the presence of the NADPH:protochlorophyllide oxidoreductase (POR, EC.1.6.99.1) was not promoted by the cytokinin, leading to the conclusion that BAP maintains the level of Chl, preventing its degradation, rather than inducing Chl biosynthesis. The internal structure of chloroplasts was maintained in BAP-treated leaves for up to 6 d, with well-organized grana thylakoids and small plastoglobuli; in contrast, chloroplasts of control leaves deteriorated rapidly from day 4 with disorganized internal membranes, and more and larger plastoglobuli. BAP increased the activities of catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) and reduced the level of H2O2 in the delayed-senescence tissue. The present research indicates that BAP reduces levels of reactive oxygen species (ROS), and enhances the activity of antioxidant enzymes (CAT, APX). Our results suggest that BAP protects the cell membranes and the photosynthetic machinery from oxidative damage during delay of senescence in the dark.
KW - Ascorbate peroxidase
KW - Catalase
KW - Chloroplast
KW - Cytokinin
KW - ROS
U2 - 10.1016/j.jplph.2007.02.003
DO - 10.1016/j.jplph.2007.02.003
M3 - Article
SN - 1618-1328
VL - 164
SP - 1572
EP - 1582
JO - Journal of Plant Physiology
JF - Journal of Plant Physiology
IS - 12
ER -