A Bistable Circuit Involving SCARECROW-RETINOBLASTOMA Integrates Cues to Inform Asymmetric Stem Cell Division

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• 作者：Alfredo Cruz-Ram¨ªrez ; Sara D¨ªaz-Trivi?o ; Ikram Blilou ; Ver?nica?A. Grieneisen ; Rosangela Sozzani ; Christos Zamioudis ; P¨¢l Miskolczi ; Jeroen Nieuwl ; Ren¨¦ Benjamins ; Pankaj Dhonukshe ; Juan Caballero-P¨¦rez ; Beatrix Horvath ; Yuchen Long ; Ari?Pekka M?h?nen ; Hongtao Zhang ; Jian Xu ; James?A.H. Murray ; Philip?N. Benfey ; Laszlo Bako ; Athanasius?F.M. Mar¨¦e ; et al.
• 刊名：Cell
• 出版年：2012
• 出版时间：31 August, 2012
• 年：2012
• 卷：150
• 期：5
• 页码：1002-1015
• 全文大小：3603 K

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Summary

In plants, where cells cannot migrate, asymmetric cell divisions (ACDs) must be confined to the appropriate spatial context. We investigate tissue-generating asymmetric divisions in a stem cell daughter within the Arabidopsis root. Spatial restriction of these divisions requires physical binding of the stem cell regulator SCARECROW (SCR) by the RETINOBLASTOMA-RELATED (RBR) protein. In the?stem cell niche, SCR activity is counteracted by phosphorylation of RBR through a cyclinD6;1-CDK complex. This cyclin is itself under transcriptional control of SCR and its partner SHORT ROOT (SHR), creating a robust bistable circuit with either high or low SHR-SCR complex activity. Auxin biases this circuit by promoting CYCD6;1 transcription. Mathematical modeling shows that ACDs are only switched on after integration of radial and longitudinal information, determined by SHR and auxin distribution, respectively. Coupling of cell-cycle progression to protein degradation resets the circuit, resulting in a ¡°flip flop¡± that constrains asymmetric cell division to the stem cell region.