A CRC–MYB chromatin loop controls auxin-mediated nectary growth in Arabidopsis

Floral nectaries, typically located at stamen bases, secrete sugar-rich nectar containing diverse secondary metabolites. Despite their defined position and specialized function, the mechanisms governing nectary formation remain unclear. Using publicly available single-nucleus RNA-seq data and newly generated spatial transcriptomic data, we identify a putative ordering of transcriptional states associated with nectary development and a spatial regulatory network controlling nectary growth in Arabidopsis thaliana . We further show that CRABS CLAW (CRC) is central to this network, integrating transcriptional regulation with spatial auxin transport and pathways controlling phytohormone signaling, sugar transport and terpene biosynthesis. CRC interacts with MYB21, MYB24 and MYB57 to form a complex that binds the 5′ and 3′ regulatory regions of MACCHI-BOU 4 ( MAB4 ), promoting a chromatin loop that enhances MAB4 expression and supports proper nectary size. MAB4 reinforces PIN-FORMED 1-mediated auxin transport to establish auxin maxima at the nectary tip and regulates PIN6 localization to maintain auxin gradients. These findings link transcriptional regulation and auxin transport with nectary organogenesis and metabolic function.