Arabidopsis ERF109 regulates auxin transport-related genes in root development

The transcription factor ERF109 acts as a crosstalk node between jasmonic acid signaling and auxin biosynthesis by directly regulating YUC2 and ASA1 during lateral root formation in Arabidopsis. However, whether ERF109 regulates the auxin transport remains unclear. Here we report a mechanism of ERF109-mediated auxin transport in root system. Through root transcriptome comparison between erf109, wild type, and 35S:ERF109, we found that the genes PIN2 and PIN4, encoding the major membrane-based efflux carriers of auxin, were enriched in the overexpression line. In the promoters of these auxin transport genes, GCC-box cis elements were found and potentially bound by ERF109. Moreover, PID, encoding a key regulator in polar auxin transport, was found upregulated in 35S:ERF109 and down regulated in erf109. Yeast-one-hybrid and chromatin immunoprecipitation assays showed that ERF109 directly bound to the GCC-box of PIN2, PIN4, and PID. Genetic analyses with double mutants confirmed the function of ERF109 in the regulation of auxin transport in Arabidopsis roots. Taken together, our results show that ERF109 modulates auxin transport by directly regulating PIN2, PIN4 and PID. This ERF109-mediated auxin transport likely works together with ERF109-mediated auxin synthesis to establish auxin maxima for lateral root initiation.