A PHABULOSA/Cytokinin Feedback Loop Controls Root Growth in Arabidopsis

作者：Dello Ioio Raffaele; Galinha Carla; Fletcher Alexander G; Grigg Stephen P; Molnar Attila; Willemsen Viola; Scheres Ben; Sabatini Sabrina; Baulcombe David; Maini Philip K; Tsiantis Miltos^*

来源：Current Biology, 2012, 22(18): 1699-1704.

DOI：10.1016/j.cub.2012.07.005

The hormone cytokinin (CK) controls root length in Arabidopsis thaliana by defining where dividing cells, derived from stem cells of the root meristem, start to differentiate [1-6]. However, the regulatory inputs directing CK to promote differentiation remain poorly understood. Here, we show that the HD-ZIPIII transcription factor PHABULOSA (PHB) directly activates the CK biosynthesis gene ISOPENTENYL TRANSFERASE 7 (IPT7), thus promoting cell differentiation and regulating root length. We further demonstrate that CK feeds back to repress both PHB and microRNA165, a negative regulator of PHB. These interactions comprise an incoherent regulatory loop in which CK represses both its activator and a repressor of its activator. We propose that this regulatory circuit determines the balance of cell division and differentiation during root development and may provide robustness against CK fluctuations.

• 出版日期2012-9-25