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SUMMARY:The sweet growth of plant cells. New players on the O-glycosylatio
 n pathway of cell wall glycoproteins. - Jose Estevez\, Universidad de Buen
 os Aires
DTSTART:20120528T100000Z
DTEND:20120528T110000Z
UID:TALK38187@talks.cam.ac.uk
CONTACT:Hannah Ambler
DESCRIPTION:The structural plasticity of carbohydrates is greater than tha
 t of amino acids but our understanding of the implications of such plastic
 ity and how it relates to a potential biological function is still limited
 . We have examined in depth the fundamental role that carbohydrates play i
 n the growth of root hairs of Arabidopsis thaliana. Root hairs are single 
 cells specialized in the absorption of water and nutrients. Growing root h
 airs require intensive cell-wall changes to accommodate cell expansion at 
 the apical end by a process known as tip growth. The cell wall of plants i
 s a very rigid structure comprised largely of polysaccharides and hydroxyp
 roline-rich glycoproteins (HRGPs) that include extensins (EXTs) and arabin
 ogalactan-proteins (AGPs). However\, during plant growth these cells incre
 ase 200 times their original size by addition of more sugars and proteins.
  It has been assumed that chemical changes of wall constituents and wall n
 etworks orchestrated by enzymes and cell-wall modifying genes are implicat
 ed in the process. To investigate the issue\, our group focused on root ha
 irs as our main cell model. Proline hydroxylation\, an early posttranslati
 onal modification of cell wall HRGPs that is catalyzed by prolyl 4-hydroxy
 lases (P4Hs)\, defines the subsequent O-glycosylation sites in EXTs (which
  are mainly arabinosylated) and AGPs (which are mainly arabinogalactosylat
 ed). We explored the biological function of P4Hs\, arabinosyltransferases\
 , and EXTs in root hair cell growth. Biochemical inhibition or genetic dis
 ruption resulted in the blockage of polarized growth in root hairs and red
 uced arabinosylation of EXTs. On the other hand\, over-expression of P4Hs 
 doubles the length and increases the density of root hairs. Our results de
 monstrate that correct O-glycosylation on EXTs is essential for cell-wall 
 self-assembly and\, hence\, root hair elongation. The changes that O-glyco
 sylated cell-wall proteins undergo during growth represent a starting poin
 t to unravel the entire biochemical pathway involved in plant growth and d
 evelopment.\nVelásquez et al 2012. Recent advances on the post-translatio
 nal modifications of EXTs and their roles in plant cell walls. Frontiers i
 n Plant Science 3(93):1-6.\nVelásquez & J.M. Estevez. Root hair sweet gro
 wth. Plant Signaling & Behavior 2011. 6 (10): 1600-1602.\nVelasquez et al.
  2011. Essential role of O-glycosylated plant cell wall extensins for pola
 rized root hair growth. Science 332\, 1401-1403. 
LOCATION:Department of Biochemistry\, Hopkins Building\, Seminar Room 1
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