Chromatin-mediated feed-forward auxin biosynthesis in floral meristem determinacy

Abstract

In flowering plants, the switch from floral stem cell maintenance to gynoecium (female structure) formation is a critical developmental transition for reproductive success. In Arabidopsis thaliana, AGAMOUS (AG) terminates floral stem cell activities to trigger this transition. Although CRABS CLAW ( CRC) is a direct target of AG, previous research has not identified any common targets. Here, we identify an auxin synthesis gene, YUCCA4 ( YUC4) as a common direct target. Ectopic YUC4 expression partially rescues the indeterminate phenotype and cell wall defects that are caused by the crc mutation. The feed-forward YUC4 activation by AG and CRC directs a precise change in chromatin state for the shift from floral stem cell maintenance to gynoecium formation. We also showed that two auxin-related direct CRC targets, YUC4 and TORNADO2, cooperatively contribute to the termination of floral stem cell maintenance. This finding provides new insight into the CRC-mediated auxin homeostasis regulation for proper gynoecium formation.

Abstract

In Arabidopsis, the AG and CRC transcription factors terminate floral stem cells and allow the emergence of female floral organs. Here the authors show that AG and CRC form a feed-forward loop that controls local auxin biosynthesis via induction of YUCCA4 to ensure successful gynoecium formation.