Generation and Characterization of a Specific Polyclonal Antibody against Arabidopsis thaliana Phytochrome-Interacting Factor 3

Phytochrome-interacting factors (PIFs) are a basic helix-loop-helix family of transcriptional regulators that maintain skotomorphogenesis and suppress photomorphogenesis. PIFs are regulated by plant photoreceptors, especially phytochromes. In general, PIFs physically interact with phytochromes, and this interaction induces PIF’s phosphorylation and subsequent degradation, contributing to the initiation of photomorphogenic development. Among the eight members of PIF (PIF1 to PIF8) reported in Arabidopsis thaliana, PIF3 is the first discovered member and plays central roles in de-etiolation and chlorophyll biosynthesis. More recently, PIF3 has been also reported to regulate hormone signaling and cold tolerance in plants. Although PIF3 protein shows dynamic behaviors in plants, its study has been limited due to the lack of an authentic PIF3 antibody. In this study, we produced polyclonal antibodies using inclusion bodies and characterized the PIF3 antibody based on specificity and sensitivity. In addition, we investigated PIF3 phosphorylation and degradation during phytochrome-mediated light signaling in plants. Furthermore, we successfully performed in vitro protein–protein interaction and co-immunoprecipitation assays between phytochrome B (phyB) and PIF3 using the antibody. Therefore, we obtained an authentic PIF3 antibody that could be used as a valuable tool to study the multi-faceted functions of PIF3.