Abstract
During seasonal cold acclimation, 18 kD proteins, designated WAP18, were accumulated in the soluble protein fractions in mulberry (Morus bombycis Koidz.) tree. The purified WAP18 showed cryoprotective activity against freeze-labile lactate-dehydrogenase, LDH, suggesting that WAP18 has roles to contribute freezing tolerance in cortical parenchyma cells of mulberry tree in winter. The cDNA cloning revealed that WAP18 has high sequence similarity to pathogenesis-related (PR)-10/Bet v 1 protein family. Northern blot analysis showed that transcript levels of WAP18 increased not only by cold treatment at 4oC but also by wounding, ethephon and salicylic acid.
It has been predicted that PR-10/Bet v 1 proteins localize in the cytosol based on the absence of apparent signal sequence. Immuno-electronmicroscpe analysis showed that gold particles against anti-WAP18 antibodies localized not only in cytosol but also in nucleus in mulberry tree. This result indicates that PR-10/Betv1 proteins localize in cytosol and nucleus.
