Chloroplastic proteins of wheat and rye grown at warm and cold-hardening temperatures

Soluble proteins and membrane polypeptides were separated from chloroplasts isolated intact from a cultivar each of spring wheat, winter wheat, and more freeze-resistant rye, and changes in them associated with cold hardening were detected by means of polyacrylamide gel electrophoresis. No drastic changes in chloroplast membrane polypeptides occurred during growth at low temperatures in the three cultivars. However, subtle changes were evident in the soluble chloroplast protein fraction. In this fraction at least one varietal difference was discernable, yet all cultivars produced a new protein band of lowest mobility during growth at low temperatures. After the preparations were fractionated by Sephadex G-50 all unhardened plant material displayed two peaks in the region of the fraction I protein band, whereas all cold-hardening material displayed one peak. A different band of soluble protein was present only after cold hardening in Kharkov whear and Puma rye, and was not present in extracts from the cold-grown spring wheat.