PLANT PHYSIOLOGY , Vol 103, Issue 2 371-377, Copyright © 1993 by American Society of Plant Biologists
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ENVIRONMENTAL AND STRESS PHYSIOLOGY |
Alteration of [beta]-Tubulin Gene Expression during Low-Temperature Exposure in Leaves of Arabidopsis thaliana
B. Chu, D. P. Snustad and J. V. Carter
Departments of Horticultural Science and Plant Biology (B.C., J.V.C.), and Department of Genetics and Cell Biology and Plant Molecular Genetics Institute (D.P.S.), University of Minnesota, St. Paul, Minnesota 55108
Responses of [beta]-tubulin gene expression to low-temperature exposure
(4[deg]C) have been investigated in leaves of Arabidopsis thaliana. During
low-temperature exposure, the patterns of both [alpha]- and [beta]-tubulin
isoforms are altered; the effect is smaller for the [alpha]-tubulins than
for the [beta]-tubulins, however. An examination of [beta]-tubulin gene
expression revealed that during low-temperature exposure, transcript levels
of TUB2, TUB3, TUB6, and TUB8 decrease, whereas those of TUB4, TUB5, and
TUB7 remain constant, and the TUB9 transcript level increases. The changes
in transcript levels of TUB6, TUB8, and TUB9 were detectable after 6 h of
low-temperature treatment. As shown by transcription-blocking experiments,
the in vivo decay rates at 25[deg]C are comparable to those at 4[deg]C for
TUB5, TUB6, and TUB8 mRNAs, whereas TUB9 mRNA appears to be more stable at
4[deg]C than at 25[deg]C. Thus, decreases in transcript levels of TUB6 and
TUB8 in response to low temperature appear to be regulated at the
transcriptional level, and the increase in TUB9 transcript level that
results from lowering the temperature from 25[deg]C to 4[deg]C may be due
in part to its slower rate of decay at 4[deg]C. When a chimeric gene
containing 1061 base pairs of TUB8 5[prime] flanking DNA fused to the
[beta]-glucuronidase coding region was used to produce transgenic
Arabidopsis plants, the chimeric gene expression was down-regulated in
response to low temperature as assayed by histochemical localization and
RNA gel blots. These results confirm that the alteration of transcript
levels of TUB8 in response to low temperature is regulated at the
transcriptional level.
