THE EFFECTS OF COLD-TEMPERATURE STRESS ON GENE-EXPRESSION IN MAIZE

A rapid decrease from the 28.degree. C incubation temperature of 5-day-old maize seedlings induced a response recorded as an altered synthesis of several polypeptides. The maximum response occurred at 4.degree. C and included cold-shock proteins with relative molecular masses of 94, 92, 90, 73, 70, 54, 50, 44, 38, 34, 33, 32, 24, 20, and 14 kilodaltons (kDa). Western bolt analysis (probed with polyclonal antibodies against maize heat-shock proteins) and fluorograms prepared from one-dimensional gel electrophoresis of maize heat-shock proteins revealed differences between the cold-induced polypeptides and the maize heat-shock proteins. The abundance of low molecular weight polypeptides and the absence of a marked depression in normal protein synthesis were the most noted differences from the heat-shock response. The cold-shock response, which was induced by as little as a 3.degree. C reduction in temperature, showed some transitory proteins, was separate from an acclimation response, and lasted up to 18 h (after returning the seedlings to 28.degree. C) before the normal protein synthetic pattern returned. Seedlings allowed to recover from a 4.degree. C shock for 4 h at 28.degree. C showed synthesis of a 250-kDa polypeptide, which lasted less than 2 h and was completely inhibited by actinomycin D.