Cryoprotective activity of winter- accumulating WAP27 protein from mulberry cortical parenchyma cells

Abstract

Freezing tolerance of cortical parenchyma cells of mulberry (Morus bombycis) drastically increases in winter. 27-kDa group 3 late embryogenesis protein (WAP27) accumulated in ER of the cells in winter.
In natural conditions, plants are subjected to prolonged freezing that at high subzero temperature results in prolonged exposure of cells to concentrated solutions. We therefore examined cryoprotection of recombinant WAP27 (rWAP27) on lactate dehydrogenase (LDH) activity against prolonged freezing. The rWAP27 preserved above 80% of LDH activity during prolonged freezing at -2, -4, -10, -20^oC. The cryoprotective activity of bovine serum albumin was nearly equal to that of rWAP27 during prolonged freezing at -20^oC, but decreased with freezing time at -2 and -4^oC. The cryoprotective activity of ovalbumin was also decreased with freezing time at -2 to -20^oC. The rWAP27 has a high cryoprotective activity to freeze-labile proteins against prolonged freezing.