Soluble Proteins Induced by Low Temperature Treatment in the Leaves of Spring and Winter Wheat Cultivars

Quantitative and qualitative changes in total leaf soluble proteins were determined in a spring cv. Zagross and in a winter cv. Azar 2 cultivar of allohexaploid wheat (Triticum aestivum L.) exposed to 4°C for two weeks. The data obtained were used to test whether these different genotypes of wheat responded differentially to cold treatment. Seedlings were grown in a controlled growth chamber for 14 d at 20°C and then transferred to 4°C for 14 d before returning them to 20°C (cold treatment), or else they were maintained continuously at 20°C (control treatment). The plants were sampled every 48 h for total leaf fresh weight measurements. Total leaf soluble proteins were extracted. Proteins concentration was either determined by a colorimetric method, or size-fractionated on SDS-PAGE. Clear cold-induced increases in proteins quantity occurred during the low temperature treatment irrespective of cultivar. However, the electrophoretic protein patterns showed differences between-cultivar and between-temperature treatment. Ten new cold-induced polypeptides (17, 19, 30, 77, 83, 90, 100, 166, 180 and 200 kDa) were produced from 2 d at 4°C reaching their maximum amounts on 6-10 d at 4°C regardless of cultivar. With increasing exposure to 4°C, fewer new cold-induced higher molecular weight (HMW) polypeptides (166, 180 and 200 kDa) was observed compared with those produced over the first week regardless of cultivar. During the second week, many new cold-induced lower molecular weight (LMW) polypeptides were detected at 4°C. This alteration in polypeptide composition from HMW to LMW occurred about 4 d earlier in the cold-treated seedlings of winter wheat compared with spring wheat. Perhaps cold-shock proteins are a component of this coldinduced response.