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Gayana. Botánica

On-line version ISSN 0717-6643

Abstract

GALLARDO-CERDA, Jorge; BRAVO, León A  and  CORCUERA, Luis J. Leaf seasonal accumulation of a 47-kDa dehydrin and changes in its cryoprotective activity in Nothofagus dombeyi (Mirb.) Blume. Gayana Bot. [online]. 2012, vol.69, n.1, pp.1-8. ISSN 0717-6643.  http://dx.doi.org/10.4067/S0717-66432012000100002.

Nothofagus dombeyi (Mirb.) Blume is an evergreen tree, pioneer in habitats subject to unfavorable environmental conditions as nighttime freezing temperatures and low water content. It inhabits zones characterized by cold Winter with freezing temperature and Spring frosts reaching to -5°C. Furthermore, it has the capacity to maintain a functional photosynthetic apparatus at low temperatures. We postulated that N. dombeyi is capable to accumulate dehydrins in leaves in response to cold. Seasonal variation in dehydrins, soluble total proteins, and cryoprotective activity in vitro of protein extracts of N. dombeyi leaves were analyzed during the years 2004 and 2005. A dehydrin-like protein of 47-kDa was immunologically identified; this protein was present only in Winter and Spring. The highest accumulation of this protein and the maximal in vitro cryoprotective activity was found during Spring. The leaf total protein extract of this season preserved the 100% of lactate dehydrogenase (LDH) enzyme activity after 5 freeze/thaw cycles in liquid nitrogen adding 10 μg/ml of total proteins extract. The soluble protein concentration increased from 1.8 mg/g in Summer to 4.8 mg/g in Fall on base of fresh weight, and declined through Winter and Spring. The 47-kDa dehydrin may be related to cold hardiness of leaf tissue in overwintering N. dombeyi. We conclude that cell dehydration caused by freezing is the main factor involved in the triggering of 47-kDa dehydrin accumulation in leaves of N. dombeyi. The accumulation of reactive oxygen species (ROS) by oxidative stress product of high irradiance and frosts during Spring, and their role in the triggering of the 47-kDa dehydrin accumulation in leaves of N. dombeyi is discussed.

Keywords : Evergreen; tree; old acclimation; proteins.

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