Heat treatment results in a loss of transgene-encoded activities in several tobacco lines.

摘要

Heat treatment (37鳦) of transgenic tobacco (Nicotiana tabacum) plants led to a reversible reduction or complete loss of transgene-encoded activities in about 40% of 10 independent transformants carrying the luciferase-coding region fused to the 35Scauliflower mosaic virus or the soyabean small subunit promoter and the nopaline synthase promoter driving the neomycin phosphotransferase gene, whereas the other lines had temperature-tolerant activities. Temperature sensitivity or tolerance of transgene-encoded activities was heritable. In some of the lines, temperature sensitivity of the transgene-encoded activities depended on the stage of development, occurring in either seedlings (40% luciferase and 50% neomycin phosphotransferase) or adult plants (both 40%). The phenomenon did not correlate with copy numbers or the homo- or hemizygous state of the transgenes. In lines harbouring a temperature-sensitive luciferase activity, reduction of bioluminescence was observed after 2-3 h at 37鳦. Activitywas regained after 2 h of subsequent cultivation at 25鳦. Irrespective of the reaction to the heat treatment, the level of luciferase RNA was slightly increased at 37鳦. Only in lines showing temperature sensitivity of transgene-encoded activities was the amount of luciferase and neomycin phosphotransferase strongly reduced. In sterile culture, heat treatment for 15 d did not cause visible damage or changes in plant morphology. In all plants tested a slight induction of the heat-shock response was observed at 37鳦.