Rice phytochrome-interacting factor protein OsPIF14 represses OsDREB1B gene expression through an extended N-box and interacts preferentially with the active form of phytochrome B

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.

Phytochromes and Phytochrome Interacting Factors

“…Among rice PILs, only OsPIL14 has been shown to interact with OsphyA, OsphyB, and OsphyC, but it interacts preferentially with OsphyB in vitro ( Fig. 1; Cordeiro et al, 2016). Similar to Arabidopsis PIFs, the overexpression of OsPILs also promotes hypocotyl and internode elongation in Arabidopsis and rice, respectively (Nakamura et al, 2007;Todaka et al, 2012).…”

Phytochrome Interacting Factors (PIFs) in Solanum lycopersicum: Diversity, Evolutionary History and Expression Profiling during Different Developmental Processes

“…However, PIF genes have been lagged behind and almost exclusively studied in A . thaliana [11–14]. Besides the well described PHY-mediated proteasomal degradation mentioned above, PIF genes are under tight transcriptional regulation as indicated by database and genome-wide binding site analyses for several A .…”

“…PIFs are basic helix–loop–helix (bHLH) transcription factors that play a key role in PHY-mediated light signal transduction being part of the regulatory network of a wide range of developmental processes, from seed germination towards senescence. However, with few exceptions [11–14], PIFs have been only studied in A . thaliana .…”

Phytochrome B Negatively Affects Cold Tolerance by Regulating OsDREB1 Gene Expression through Phytochrome Interacting Factor-Like Protein OsPIL16 in Rice

“…PhyB deficiency alleviated chilling-induced photoinhibition in rice, probably through a more stabilized chloroplast structure and higher unsaturated fatty acid content in membrane lipids in the phyB mutant (Yang et al, 2013). Cordeiro et al (2016) observed that OsPIF14 could bind to the OsDREB1B promoter through two N-boxes (CACG(A/C)G) and that the flanking regions of the hexameric core were essential for protein-DNA interaction and stability. Transactivation assays using Arabidopsis protoplasts and rice protoplasts showed that OsPIF14 downregulates OsDREB1B gene expression (Cordeiro et al, 2016).…”

“…Cordeiro et al (2016) observed that OsPIF14 could bind to the OsDREB1B promoter through two N-boxes (CACG(A/C)G) and that the flanking regions of the hexameric core were essential for protein-DNA interaction and stability. Transactivation assays using Arabidopsis protoplasts and rice protoplasts showed that OsPIF14 downregulates OsDREB1B gene expression (Cordeiro et al, 2016). Furthermore, yeast two-hybrid and Co- immunoprecipitation analyses revealed that OsPIF14 preferentially binds to the active Pfr form of rice phyB (Cordeiro et al, 2016).…”