PLANT PHYSIOLOGY , Vol 115, Issue 3 939-947, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Heat Treatment Results in a Loss of Transgene-Encoded Activities in Several Tobacco Lines
K. Neumann, W. Droge-Laser, S. Kohne and I. Broer
Universitat Bielefeld, Fakultat fur Biologie, Lehrstuhl fur Genetik, Postfach 100131, 33501 Bielefeld, Germany
Heat treatment (37[deg]C) 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 35S cauliflower mosaic virus or the
soybean 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 harboring a temperature-sensitive luciferase activity,
reduction of bioluminescence was observed after 2 to 3 h at 37[deg]C.
Activity was regained after 2 h of subsequent cultivation at 25[deg]C.
Irrespective of the reaction to the heat treatment, the level of luciferase
RNA was slightly increased at 37[deg]C. 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[deg]C.
