[Seminars] PSB event reminder

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Calendar Name: seminars
Scheduled for: Friday, December 17 2010, 11:00 - 12:30
Event text:    Alexis Maizel
	       
	       Department of Stem Cell Biology
	       Center for organismal studies
	       University of Heidelberg 
	       
	       Heidelberg
	       GERMANY
Details:       "Control of developmental plasticity and robustness by
	       small RNAs in Arabidopsis"
	       
	       ABSTRACT
	       Plants adapt to their environment by forming new organs
	       throughout their entire postembryonic life. The
	       harmonious growth of these organs in response to
	       morphogenetic signals is essential. Lateral roots
	       unceasingly branch from the main root in response to
	       local auxin maxima. How a local maximum translates to a
	       robust pattern of gene activation ensuring the proper
	       growth of the newly formed root is not known. The
	       TAS3-derived trans-acting siRNAs (ta-siRNAs) belong to a
	       plant-specific class of endogenous small RNAs, whose
	       biogenesis requires the initial microRNA 390
	       (miR390)-mediated cleavage of the TAS3 precursor by
	       AGO7. The ta-siRNAs target mRNAs encoding ARF3/ETTIN and
	       ARF4 which are transcription factors of the AUXIN
	       RESPONSE FACTORs that mediate the effects of auxin. I
	       will present recent results establishing that auxin
	       maxima at the sites of lateral root initiation promote
	       localised production of miR390, allowing the formation
	       of ta-siARFs to subsequently inhibit ARF3/4 activity in
	       the incipient primordia. In turn, ARF3 and ARF4
	       contribute both positively and negatively to miR390
	       accumulation. These results support a model in which
	       small RNAs employ target genes to regulate their own
	       production.

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