An Arabidopsis mutation in translation elongation factor 2
causes superinduction of CBF/DREB1 transcription factor genes but blocks the
induction of their downstream targets under low temperatures.
Guo Y, Xiong L, Ishitani M, Zhu JK.
Department of Plant Sciences, University of Arizona, Tucson, AZ 85721, USA.
Low temperature regulates gene expression in bacteria, yeast, and animals as
well as in plants. However, the signal transduction cascades mediating the low
temperature responses are not well understood in any organism. To identify
components in low temperature signaling genetically, we isolated Arabidopsis
thaliana mutants in which cold-responsive genes are no longer induced by low
temperatures. One of these mutations, los1-1, specifically blocks low
temperature-induced transcription of cold-responsive genes. Surprisingly,
cold-induced expression of the early response transcriptional activators,
C-repeat/dehydration responsive element binding factors (CBF/DREB1s), is
enhanced by the los1-1 mutation. The los1-1 mutation also reduces the capacity
of plants to develop freezing tolerance but does not impair the vernalization
response. Genetic analysis indicated that los1-1 is a recessive mutation in a
single nuclear gene. The LOS1 gene encodes a translation elongation factor
2-like protein. Protein labeling studies show that new protein synthesis is
blocked in los1-1 mutant plants specifically in the cold. These results reveal a
critical role of new protein synthesis in the proper transduction of low
temperature signals. Our results also suggest that cold-induced transcription of
CBF/DREB1s is feedback inhibited by their gene products or by products of their
downstream target genes.