The role of superoxide dismutase activity in response to cold acclimation in potato

Abstract

Transcript accumulation and protein activation of superoxide dismutase (SOD) isoenzymes were studied during cold acclimation in potato genotypes of varying degrees of freezing tolerance. In all genotypes studied, 2 days of cold acclimation led to increased SOD activity in concert with improved freezing tolerance. In freezing-tolerant Solanum commersonii Dun. (SCMM), the increase was most probably due to enhanced CuZnSOD isoenzyme activity. Compared to freezing sensitive S. tuberosum (SPV11), only slightly higher SOD activity was detected in SCMM. In potato hybrids (S. commersonii×S. tuberosum SPV11) there was no correlation between SOD activity and freezing tolerance. Although freezing tolerance continued to improve up to 7 days during cold acclimation, elevated SOD levels were measured only in two potato hybrids. Thus, the genotype's freezing tolerance or cold acclimation capacity was not related to the level of SOD activity. Mitochondrial MnSOD transcript, accumulated in potato genotypes which were able to cold acclimate although elevated MnSOD isoenzyme activity, was not always detected. The MnSOD transcript accumulation was probably an indicator of mitochondrial activity during cold acclimation. These results suggest that although SOD activity may contribute to the freezing tolerance and acclimation capacity, traits other than SOD activity were more important for the expression of freezing tolerance in potato hybrids.