The content, composition and biological activity of polysomes from three wheat genotypes were studied during cold acclimation. The structural integrity of the different polysome populations was not affected by the hardening temperature. Polysomes were also found to accumulate at higher level in cold hardened seedlings suggesting a high protein synthesis capacity during the acclimation period. The in vitro translation of polysome-bound mRNAs in the wheat germ cell-free system showed a high translation potential of polysomes from cold hardened seedlings compared to that of control. The electrophoretic analysis of the translation products by two-dimensional SDS-PAGE revealed the induction of several new mRNAs in cold hardened wheat seedlings. The presence of these new messengers in the polysomal fraction suggests that new messages have already been processed, transported and preferentially selected for translation by the ribosomes. The most important change was the induction and pronounced synthesis of four peptides one high mol wt peptide of 200 kDa (pI 6.5) and three smaller ones of 58 (pI 7.0), 48 (pI 7.1) and 48 (pI 7.2) kDa respectively in the freezing tolerant cultivar Norstar. These specific polypeptides were absent in the freezing sensitive cultivar Glenlea suggesting that their induction and expression was associated with the freezing tolerance capacity.
展开▼
