Characterization of Ribes rubrum callus cultured under low temperature

Ribes rubrum callus was cultured at the temperature of 15 degrees C for 28 d. The contents of proteins and lipids in the callus cultured at 15 degrees C in a 28 d culture was significantly increased, being 1.1- and 1.2-fold, respectively, of those in callus cultured at 25 degrees C. Comparisons of the contents of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG) and phosphatidyldiacylglycerol (PG) revealed that in the callus cultured at 25 degrees C, the content of MGDG was significantly decreased and those of the others significantly increased compared to those in callus cultured at 15 degrees C, in a 7 d culture. But, in a 28 d culture, the contents of these lipids in callus at 15 degrees C became the same as those in callus cultured at 25 degrees C. In regard to the protein composition, the contents of proteins 30 KDa or less in callus cultured at 15 degrees C in a 28 d culture were significantly higher than those in callus cultured at 25 degrees C. These consequences reflect that not only increase in the polyunsaturated fatty acid (PUFA) ratio of total fatty acid (TFA) with cold treatment reported by us previously [Hirano, M., J. Ferment. Bioeng., 83, 608-611 (1997)], but also an increase in low-molecular-weight protein content might be responsible for the cold-tolerance of R. rubrum callus.