JXB Advance Access originally published online on May 19, 2006
Journal of Experimental Botany 2006 57(8):1759-1768; doi:10.1093/jxb/erl007
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RESEARCH PAPER |
Senescence- and drought-related changes in peroxidase and superoxide dismutase isoforms in leaves of Ramonda serbica
1Center for Multidisciplinary Studies, Belgrade University, Kneza Vi
eslava 1a, 11030 Belgrade, Serbia and Montenegro
2Faculty of Biology, Belgrade University, Takovska, 11000 Belgrade, Serbia and Montenegro
3Dipartimento di Chimica e Biotecnologie Agrarie, Università degli Studi di Pisa, Via del Borghetto, 80, 56124 Pisa, Italy
*To whom correspondence should be addressed. E-mail: fnavari{at}agr.unipi.it
Ramonda sp. (Gesneriaceae) is an endemic and relic plant in a very small group of poikilohydric angiosperms that are able to survive in an almost completely dehydrated state. Senescence- and drought-related changes in the activity of peroxidase (POD; EC 1.11.1.7 [EC] ), ascorbate peroxidase (EC 1.11.1.11 [EC] ), and superoxide dismutase (SOD; EC 1.15.1.1 [EC] ) were determined in leaves of different age and relative water content. The results indicate that different POD isoforms were stimulated during senescence and dehydration. Two of the soluble POD isoforms were anionic with pI 4.5, and two were cationic with pI 9.3 and 9.0. The activity of ascorbate peroxidase remained unchanged either by drought or senescence. For the first time, SOD isoforms have now been determined in this resurrection plant. Several SOD isoforms, all of the Mn type, were found to be anionic with pI 4 and a few others had pI from 5 to 6, while one band of FeSOD with a lower molecular weight was neutral. Rehydration brought about a remarkable decrease over the first hour in the activity of all the antioxidant enzymes examined but activity recovered 1 d after rehydration. The results confirmed that dehydration and senescence caused disturbance in the redox homeostasis of Ramonda leaves, while inducing different POD isoforms. A physiological role of peroxidase reaction with hydroxycinnamic acids in conservation and protection of cellular constituents of desiccated Ramonda leaves is suggested.
Key words: Desiccation, peroxidase, Ramonda, senescence, superoxide dismutase