Functional dissection of theARGONAUTE7promoter

AbstractARGONAUTES are the central effector proteins of RNA silencing which bind target transcripts in a small RNA-guided manner.Arabidopsis thalianahas tenARGONAUTE(AGO) genes, with specialized roles in RNA-directed DNA methylation, post-transcriptional gene silencing, and antiviral defense. To better understand specialization amongAGOgenes at the level of transcriptional regulation we tested a library of 1497 transcription factors for binding to the promoters ofAGO1, AGO10, andAGO7using yeast 1-hybrid assays. A ranked list of candidate DNA-binding TFs revealed binding of theAGO7promoter by a number of proteins in two families: the miR156-regulated SPL family and the miR319-regulated TCP family, both of which have roles in developmental timing and leaf morphology. Possible functions for SPL and TCP binding are unclear: we showed that these binding sites are not required for the polar expression pattern ofAGO7, nor for the function ofAGO7in leaf shape. NormalAGO7transcription levels and function appear to depend instead on an adjacent 124-bp region. Progress in understanding the structure of this promoter may aid efforts to understand how the conserved AGO7-triggeredTAS3pathway functions in timing and polarity.