Cold-inducible Transcription Factor, CaCBF, Is Associated with a Homeodomain Leucine Zipper Protein in Hot Pepper (Capsicum annuum L.)

C-Repeat/drought responsive element binding factor (CBF1/DREB1b) is a well known transcriptional activator that is induced at low temperature and in turn induces the CBF regulon (CBF-targeted genes). We have cloned and characterized two CBF1-like cDNAs, CaCBF1A and CaCBF1B, from hot pepper. CaCBF1A and CaCBF1B were not produced in response to mechanical wounding or abscisic acid but were induced by low-temperature stress at 4°C. When plants were returned to 25°C, their transcript levels of the CBF1- like genes decreased markedly within 40 min. Longterm exposure to chilling resulted in continuous expression of these genes. The critical temperature for induction of CaCBF1A was between 10 and 15°C. Low temperature led to its transcription in roots, stems, leaves, fruit without seeds, and apical meristems, and a monoclonal antibody against it revealed a significant increase in CaCBF1A protein by 4 h at 4°C. Twohybrid screening led to the isolation of an homeodomain leucine zipper (HD-Zip) protein that interacts with CaCBF1B. Expression of HD-Zip was elevated by low temperature and drought. KCI Citation Count: 24