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Title: Rice phytochrome-interacting factor protein OsPIFff14 represses OsDREB1B gene expression through an extended N-box and interacts preferentially with the active form of phytochrome B

Author
item CORDEIRO, A - University Of California
item FIGUEIREDO, D - University Of California
item TEPPERMAN, J.M. - University Of California
item BORBA, R. - University Of California
item LOURENCO, T - University Of California
item ABREAU, I - University Of California
item OUWERKERK, P.B. - University Of California
item QUAIL, P.H. - University Of California
item OLIVIRA, M.M. - University Of California
item SAIBO, N.J.M. - University Of California

Submitted to: Biochimica et Biophysica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2014
Publication Date: 10/21/2014
Citation: Cordeiro, A., Figueiredo, D., Tepperman, J., Borba, R., Lourenco, T., Abreau, I., Ouwerkerk, P., Quail, P., Olivira, M., Saibo, N. 2014. Rice phytochrome-interacting factor protein OsPIFff14 represses OsDREB1B gene expression through an extended N-box and interacts preferentially with the active form of phytochrome B. Biochimica et Biophysica Acta. 1859(2):393-404.

Interpretive Summary: Plants have evolved several mechanisms to cope with adverse environmental conditions. DREB1/CBF genes are rapidly and transiently induced by low temperatures and have been described as major regulators of stress responses. To better understand the transcriptional network involved in cold signaling in rice, we used a Yeast One-Hybrid system to identify transcription factors that bind physically to the regulatory promoter region of a gene called OsDREB1B. We identified a Phytochrome (phy)-Interacting bHLH Factor we called OsPIF4, and showed that it binds to phyB and represses gene expression. Collectively, our results suggest that OsPIF4 is involved in the cross-talk between light and stress signaling through interaction with the OsDREB1B promoter.

Technical Abstract: DREB1/CBF genes, known as major regulators of plant stress responses, are rapidly and transiently induced by low temperatures. Using a Yeast one Hybrid screening, we identified a putative Phytochrome-Interacting bHLH Factor (OsPIF14), as binding to the OsDREB1B promoter. bHLH proteins are able to bind to hexameric E-box (CANNTG) or N-box (CACG(A/ C)G) motifs, depending on transcriptional activity. We have shown that OsPIF14 binds to the OsDREB1B promoter through two N-boxes and that the flanking regions of the hexameric core are essential for protein-DNA interaction and stability. We also showed that OsPIF14 down-regulates OsDREB1B gene expression in rice protoplasts, corroborating the OsPIF14 repressor activity observed in the transactivation assays using Arabidopsis protoplasts. In addition, we showed that OsPIF14 is indeed a Phytochrome Interacting Factor, which preferentially binds to the active form (Pfr) of rice phytochrome B. This raises the possibility that OsPIF14 activity might be modulated by light. However, we did not observe any regulation of the OsDREB1B gene expression by light under control conditions. Moreover, OsPIF14 gene expression was shown to be modulated by different treatments, such as drought, salt, cold and ABA. Interestingly, OsPIF14 showed also a specific cold-induced alternative splicing. All together, these results suggest the possibility that OsPIF14 is involved in cross-talk between light and stress signaling through interaction with the OsDREB1B promoter. Although in the absence of stress, OsDREB1B gene expression was not regulated by light, given previous reports, it remains possible that OsPIF14 has a role in light modulation of stress responses.