Characterization of an 80-kDa dehydrin-like protein in barley responsive to cold acclimation

Barley (Hordeum vulgare L.) exposed to low temperature increases its freezi ng tolerance. This increase has been associated with several metabolic chan ges caused by low temperature, including expression of dehydrins (DHN), a f amily of proteins induced by dehydration and cold acclimation, DHNs play an undetermined role in dehydration responses during freezing. We have studie d the accumulation of an 80-kDa DHN-like protein (P-80) in barley under col d acclimation 6/4 degrees C (day/night), postulating that it is localized i n tissues where primary ice nucleation occurs. P-80 was absent in nonacclim ated plants and was detectable after 48 h of cold acclimation, reaching a s table level after 6 days. P-80 decreased when plants were returned to 20-25 degrees C. Drought, ABA and high temperature did not increase the levels o f P-80, suggesting that its expression could be specifically regulated by c old. Immunolocalization by tissue printing and fresh cross sections of leav es showed the protein to be associated with vascular tissues and epidermis. The localization of P-80 is consistent with our hypothesis because vascula r tissue and the epidermis are preferential ice nucleation zones during the onset of freezing, The differential accumulation of P-80 may have an adapt ive value by participating in tolerance mechanisms during freeze-induced de hydration.