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Calendar Name: seminars
Scheduled for: Friday, September 2 2011, 14:00 - 15:30
Event text:    Dr Martin Crespi
	       
	       Institut des Sciences Végétales
	       CNRS
	       Université Paris
	       
	       Gif sur Yvette/Paris
	       FRANCE
Details:       “Impact of non-coding RNAs in root developmental
	       plasticity”
	       
	       ABSTRACT
	       Long non-protein coding RNAs (npcRNA) represent an
	       emerging class of riboregulators, which act either
	       directly in this long form or are processed to shorter
	       miRNA and siRNAs. Plant and animals use small RNAs
	       (microRNAs and siRNAs) as guide for post-transcriptional
	       and epigenetic regulation. In plants, miRNAs and
	       trans-acting siRNA (tasiRNA) result from different
	       biogenesis pathways but both interact with target
	       transcripts to direct their cleavage. Genome-wide
	       bioinformatic analysis of full-length cDNA databases
	       allowed us to identify 76 Arabidopsis long npcRNAs.
	       Eleven npcRNAs were antisense to protein-coding mRNAs
	       whereas certain corresponded to miRNA or siRNA
	       precursors. In addition, numerous 24-nt siRNAs matched
	       to five different npcRNAs. To link them to root
	       developmental plasticity, we have shown that abiotic
	       stresses and hormone treatments in roots altered the
	       accumulation of 22 of these npcRNAs.
	       Functional studies are ongoing to understand the
	       regulatory mechanisms involving npcRNAs and their
	       interacting RNA binding proteins in root tissues. We
	       have identified an RNA-binding protein that interacts
	       with an npcRNA that accumulates in nuclear “speckles”
	       and controls auxin responses. In addition, one npcRNA
	       expressed in root tissues corresponded to TAS3a, a
	       tasiRNA precursor target of miR390. A feedback mechanism
	       involving miR390/tasiRNAs and their ARF targets
	       quantitatively controls lateral root emergence. Finally,
	       the npcRNA43 locus was transcribed in sense/antisense
	       orientation and its overexpression led to a
	       developmental phenotype suggesting a novel compensatory
	       mechanism mediated by an antisense RNA to control gene
	       expression. We think that environmental control of long
	       and small npcRNAs through interactions with RBPs may
	       fine tune expression patterns of regulatory genes to
	       modulate root developmental plasticity.

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