A High-Throughput Screening System for Arabidopsis Transcription Factors and Its Application to Med25-Dependent Transcriptional Regulation

The activities of transcription factors （TFs） require interactions with specific DNA sequences and other reg- ulatory proteins. To detect such interactions in Arabidopsis, we developed a high-throughput screening system with a Gateway-compatible Gal4-AD-TF library of 1589 Arabidopsis TFs, which can be easily screened by mating-based yeast-one-hybrid （YIH） and yeast-two-hybrid （Y2H） methods. The efficiency of the system was validated by examining two well-characterized TF-DNA and TF-protein interactions： the CHE-CCA1 promoter interaction by YIH and NPR1-TGAs interactions by Y2H. We used this system to identify eight TFs that interact with a Mediator subunit, Med25, a key reg- ulator in JA signaling. We identified five TFs that interacted with the GCC-box cis-element in the promoter of PDF1.2, a downstream gene of Med25. We found that three of these TFs, all from the AP2-EREBP family, interact directly both with Med25 and the GCC-box of PDF1.2, suggesting that Med25 regulates PDF1.2 expression through these three TFs. These results demonstrate that this high-throughput Y1H/Y2H screening system is an efficient tool for studying transcrip- tional regulation networks in Arabidopsis. This system will be available for other Arabidopsis researchers, and thus it provides a vital resource for the Arabidopsis community.