Control of stem cell niche and fruit development inArabidopsis thalianabyAGO10/ZWLrequires the bHLH transcription factorINDEHISCENT

AbstractBackgroundThe shoot apical meristem (SAM) in plants is composed of a small mound of pluripotent stem cells that generate new organs. ARGONAUTE10 (AGO10) is known to be critical for maintenance of the embryonic SAM by regulating the expression ofClass III HOMEODOMAIN-LEUCINE ZIPPER(HD-ZIP III) transcription factors, which then modulate downstream responses to the key phytohormone auxin. However, we do not understand how AGO10 modulates auxin responses after embryogenesis in the mature plant.ResultsHere we show thatAGO10regulates auxin responses in the post-embryonic SAM via the bHLH transcription factorINDEHISCENT(IND). IND directly regulates auxin responses in the SAM regulating the auxin transporter PIN1 via direct transcriptional regulation ofPINOIDkinase. We show that a loss of functionindmutation significantly restoresago10zwl-3mutant SAM and fruit phenotypes.ago10zwl-3mutants overexpressINDand overexpression of IND phenocopies theago10zwl-3SAM phenotypes, and regulates auxin transport and responses in the SAM. AGO10 also regulates post-embryonic development in the fruit via a similar genetic pathway.ConclusionsWe characterise a molecular mechanism that is conserved during post embryonic development linkingAGO10directly to auxin responses.