Plants' lifelong growth and organ formation are dependent on the activity of pluripotent stem cells. In the root apical meristem (RAM) of Arabidopsis thaliana, stem cells surround a small group of less active cells, the Quiescent Center (QC). The QC, together with its surrounding stem cells, forms the root stem cell niche. Recent work has shown that local auxin levels mediate maintenance or differentiation of distal stem cells (DSC) in the root meristem (Ding and Friml, 2010). Auxin signalling for differentiation of DSC requires the IAA17/AXR3, ARF10 and ARF16 transcriptional regulators. The auxin response factors ARF10 and ARF16 repress WOX5, a major controller of root stem cell maintenance, and restrict it to the QC, where WOX5 activity is required for the expression of PLT1, a master regulator of root development (Ding and Friml, 2010). However, more insights are needed to unravel the network of transcription factors controlling the activity of distal stem cells. Here we show that the ATHB2, ATHB4 and HAT3 HD-Zip II transcription factors - known to play a crucial role in apical embryo development (Turchi et al., 2013) - are required for distal stem cell maintenance in the RAM, as demonstrated by promotion and inhibition of DSC differentiation in the hat3 athb4 athb2 triple mutant and in the HAT3 overexpressors, respectively. Furthermore, we find that, compared to controls, the athb2 athb4 hat3 triple loss-of-function mutant displays an increased DR5rev::GFP signal in the distal stem cells, whereas it does not show any significant difference in GFP intensity in the QC. Taken together, our data indicate that HD-Zip II proteins contribute to the establishment and/or maintenance of a graded auxin response in the root stem cell niche. Ding Z and Friml J. (2010). Auxin regulates distal stem cell differentiation in Arabidopsis roots. Proc. Natl. Acad. Sci. USA 107:12046-12051. Turchi L, Carabelli M, Ruzza V, Possenti M, Sassi M, Peñalosa A, Sessa G, Salvi S, Forte V, Morelli G and Ruberti I (2013). Arabidopsis HD-Zip II transcription factors control apical embryo development and meristem function. Development 140:2118-2129.
HD-Zip II transcription factors regulate distal stem cell maintenance in the Arabidopsis root
Turchi L;Carabelli M;Sessa G;Ruberti I
2014
Abstract
Plants' lifelong growth and organ formation are dependent on the activity of pluripotent stem cells. In the root apical meristem (RAM) of Arabidopsis thaliana, stem cells surround a small group of less active cells, the Quiescent Center (QC). The QC, together with its surrounding stem cells, forms the root stem cell niche. Recent work has shown that local auxin levels mediate maintenance or differentiation of distal stem cells (DSC) in the root meristem (Ding and Friml, 2010). Auxin signalling for differentiation of DSC requires the IAA17/AXR3, ARF10 and ARF16 transcriptional regulators. The auxin response factors ARF10 and ARF16 repress WOX5, a major controller of root stem cell maintenance, and restrict it to the QC, where WOX5 activity is required for the expression of PLT1, a master regulator of root development (Ding and Friml, 2010). However, more insights are needed to unravel the network of transcription factors controlling the activity of distal stem cells. Here we show that the ATHB2, ATHB4 and HAT3 HD-Zip II transcription factors - known to play a crucial role in apical embryo development (Turchi et al., 2013) - are required for distal stem cell maintenance in the RAM, as demonstrated by promotion and inhibition of DSC differentiation in the hat3 athb4 athb2 triple mutant and in the HAT3 overexpressors, respectively. Furthermore, we find that, compared to controls, the athb2 athb4 hat3 triple loss-of-function mutant displays an increased DR5rev::GFP signal in the distal stem cells, whereas it does not show any significant difference in GFP intensity in the QC. Taken together, our data indicate that HD-Zip II proteins contribute to the establishment and/or maintenance of a graded auxin response in the root stem cell niche. Ding Z and Friml J. (2010). Auxin regulates distal stem cell differentiation in Arabidopsis roots. Proc. Natl. Acad. Sci. USA 107:12046-12051. Turchi L, Carabelli M, Ruzza V, Possenti M, Sassi M, Peñalosa A, Sessa G, Salvi S, Forte V, Morelli G and Ruberti I (2013). Arabidopsis HD-Zip II transcription factors control apical embryo development and meristem function. Development 140:2118-2129.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
