Elongator is required for root stem cell maintenance by regulatingSHORT ROOTtranscription

SHORTROOT (SHR) is essential for stem cell maintenance and radial patterning in Arabidopsis thaliana roots, but how its expression is regulated is still unknown. Here, we report that Elongator regulates the transcription of SHR . The depletion of Elongator drastically reduced SHR expression and led to defective root stem cell maintenance and radial patterning. The importance of the nuclear localization of Elongator for its functioning, together with the insensitivity of the elp1 mutant to the transcription elongation inhibitor 6-azauracil and the direct interaction of the ELP4 subunit with the C-terminal domain of RNA polymerase II (RNAPII CTD), support the notion that Elongator plays important roles in transcription elongation. Indeed, we found that ELP3 associates with the pre-mRNA of SHR and that mutation of Elongator reduces the enrichment of RNAPII on the SHR gene body. Moreover, Elongator interacted in vivo with SUPPRESSOR OF Ty4 (SPT4), a well-established transcription elongation factor that was recruited to the SHR locus. Together, these results demonstrate that Elongator acts in concert with SPT4 to regulate the transcription of SHR .