Circadian clock-associated 1 and late elongated hypocotyl regulate expression of the C-repeat binding factor (CBF) pathway in Arabidopsis.

The C-Repeat Binding Factor (CBF) cold-response pathway has a prominent role in cold acclimation, the process whereby certain plants increase tolerance to freezing in response to low nonfreezing temperatures. In Arabidopsis, the CBF pathway is characterized by rapid induction of the C-Repeat Binding Factor 1 (CBF1), CBF2, and CBF3 genes, which encode transcriptional activators, followed by induction of the CBF-targeted genes known as the "CBF regulon." Expression of the CBF regulon results in an increase in freezing tolerance.

Heat suppresses activation of an auxin-responsive promoter in cultured guard cell protoplasts of tree tobacco.

Cultured guard cell protoplasts (GCP) of tree tobacco (Nicotiana glauca) comprise a novel system for investigating the cell signaling mechanisms that lead to acquired thermotolerance and thermoinhibition. At 32 degrees C in a medium containing an auxin (1-naphthaleneacetic acid [NAA]) and a cytokinin (6-benzylaminopurine), GCP expand, regenerate cell walls, dedifferentiate, and divide. At 38 degrees C, GCP acquire thermotolerance within 24 h, but their expansion is limited and they neither regenerate walls nor reenter the cell cycle.