背景回顾：Symmetry establishment is a critical process in the development of multicellular organs and requires careful coordination of polarity axes while cells actively divide within tissues. 

研究基础：Formation of the apical style in the Arabidopsis gynoecium involves a bilateral-to-radial symmetry transition, a stepwise process underpinned by the dynamic distribution of the plant morphogen auxin. 

主要发现：Here we show that SPATULA (SPT) and the HECATE (HEC) bHLH proteins mediate the final step in the style radialisation process and synergistically control the expression of adaxial-identity genes, HOMEOBOX ARABIDOPSIS THALIANA 3 (HAT3) and ARABIDOPSIS THALIANA HOMEOBOX 4 (ATHB4). 

作用机制：HAT3/ATHB4 module drives radialisation of the apical style by promoting basal-to-apical auxin flow and via a negative feedback mechanism that finetune auxin distribution through repression of SPT expression and cytokinin sensitivity. 

结论：Thus, this work reveals the molecular basis of axes-coordination and hormonal cross-talk during the sequential steps of symmetry transition in the Arabidopsis style.

 摘 要 

对称性建立是多细胞器官发育的一个关键过程，尤其是当细胞在组织内进行活跃分裂时，需要极性轴的精细协调。拟南芥雌蕊顶端花柱的形成涉及到一个从两侧到辐射对称的转变过程，这是一个主要由植物激素生长素的动态分布所介导的逐步过程。本文中，作者发现bHLH转录因子家族的SPT和HEC蛋白介导了花柱辐射对称形成过程的最后一步，并协同控制近轴决定基因HAT3和ATHB4的表达。HAT3/ATHB4模块通过促进生长素从基部向顶端的流动，以及通过一个负反馈调节机制（通过抑制SPT表达和细胞分裂素敏感性，精细调控生长素的分布），来驱动顶端花柱的辐射对称。因此，本文的研究结果揭示了极性轴协调和激素交联在拟南芥花柱对称性转变连续过程中的分子基础。