56. Cold-induced changes in protein systhesis in rice leaves

Department of Biological Sciences, Stanford University, Stanford, CA 94305- 5020, USA

Six day old seedlings of the cold-tolerant U.S.-cultivar Calmochi-101 grown at 32/27 degrees C were shifted to 15/10 dgrees C or 11/6 degrees C for up to 7 days. Changes in protein synthesis were analysed by radiolabeling of intact leaves with ³⁵S-met, followed by extraction of the proteins, gel electrophoresis and fluorography. The overall pattern of protein synthesis during cold treatment remained similar to the control plants maintained at 32/27 degrees C. Five polypeptides (of 19,21.5,33.5,95, and 100 kd), however, were found to be stably cold-induced after one day. On the other hand, synthesis of both subunits of RuBisCo decreased continuously in the cold, to less than 50% of control values after 7 days. Synthesis of the cold-induced polypeptides ceased and RuBisCo synthesis increased after returning the plants to normal growth temperatures for one day.