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Calendar Name: seminars
Scheduled for: Monday, October 10 2011, 11:00 - 12:30
Event text:    Prof Zhenbiao Yang
	       
	       Center for Plant Cell Biology
	       Department of Botany and Plant Sciences 
	       University of California
	       
	       Riverside
	       USA
Details:       “Auxin regulates pattern formation in a self-organizing
	       and hierarchical manner in the Arabidopsis leaf
	       epidermis”
	       
	       ABSTRACT
	       Auxin regulates the formation of various developmental
	       and morphogenetic patterns in plants, but the molecular
	       and cellular mechanisms for the auxin actions are not
	       well understood. We investigate these mechanisms using
	       Arabidopsis leaf epidermal pavement cells (PCs) as a
	       model system, which form the jigsaw puzzle cell pattern
	       with interdigitated lobes and indentation.  We have
	       shown that pavement cell interdigitation is controlled
	       by localized ROP GTPase signaling, which impinges on the
	       organization of cortical actin microfilaments and
	       microtubules to generate interdigitating lobes and
	       indentations1,2.  Our recent studies indicate that auxin
	       is a localized signal that activates pavement cell
	       polarization to form lobes and coordinates lobe
	       formation with indentation formation by activating ROP
	       GTPase signaling through an Auxin-Binding Protein 1
	       (ABP1) dependent auxin perception system3. This
	       cytoplasmic auxin signaling system, which is distinct
	       from the well-established TIR1-dependent nuclear auxin
	       signaling system that regulates gene transcription,
	       modulates local coordination of lobe and indentation
	       formation within a PC and between adjacent PCs through
	       its modulation of PIN protein polarization3.  Our recent
	       work suggests that auxin also globally coordinates the
	       formation of the interdigitated PC pattern in the entire
	       leaf through a transient leaf tip- and margin-high
	       accumulation of auxin. The global coordination and the
	       auxin accumulation require the TIR1-based
	       auxin-signaling pathway that regulates gene
	       transcription.  Our findings support the hypothesis that
	       auxin acts as a self-organizing and hierarchical signal
	       in the regulation of pattern formation in the leaf
	       epidermis.  
	       
	       References
	       1.      Fu, Y., Y. Gu, Z. Zheng, G. Wasteneys, and Z.
	       Yang. 2005. Arabidopsis interdigitating cell growth
	       requires two antagonistic pathways with opposing action
	       on cell morphogenesis. Cell 120: 687-700. 
	       2.      Fu, Y.,	T. Xu, L. Zhu, and Z. Yang. 2009. A ROP
	       GTPase signaling pathway controls microtubule ordering
	       and cell expansion in Arabidopsis. Curr. Biol.
	       19:1827-32.
	       3.      Xu T, Wen M, Nagawa S, Fu Y, Chen JG, Wu MJ,
	       Perrot-Rechenmann C, Friml J, Jones AM, Yang Z. 2010.
	       Cell surface- and rho GTPase-based auxin signaling
	       controls cellular interdigitation in Arabidopsis. Cell
	       143:99-110.

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