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SUMMARY:Pollen tube growth: of male gametophytes and the need for models -
  Professor José Feijó - University of Lisbon
DTSTART:20090129T160000Z
DTEND:20090129T170000Z
UID:TALK15802@talks.cam.ac.uk
CONTACT:3901
DESCRIPTION:Pollen is the male gametophyte of plants. From a dehydrated\, 
 quiescent organ in the atmosphere\, pollen grains take up water from the f
 emale tissues in a matter of seconds\, and in minutes develop a unique for
 m of cellular outgrowth\, the pollen tube. Pollen tubes are among the fast
 est growing cells in Nature\, they achieve growth rates up to 4 um/sec\, a
 nd in a matter of few hours can increase their volume up to 50 fold withou
 t division (1). Despite copious amounts of detailed physiological and mole
 cular data\, the mechanistic regulation of growth in pollen tubes still la
 cks an integrative model. While transcriptomics reveals the presence of ab
 out 7.000 genes\, theoretical modeling shows that cooperation of all of th
 ese into two processes- wall surface and cytoplamic volume growth- is cond
 ition enough to generate apical growth as we know it. Spatial and temporal
  integration of extended biochemical and biophysical processes is mandator
 y\, and in the past we have proposed and demonstrated that "ion dynamics" 
 which we define specifically as the regulation of ion membrane fluxes and 
 cytosolic free ion concentration- is maybe a common denominator of this in
 tegrative processes\, and follow the behavior of a dynamical attractor on 
 the space phase (2). In pollen tubes\, ion fluxes are polarized\, implying
  that carriers for protons\, calcium\, chloride and potassium show non-lin
 ear patterns in space (polarized distribution of carriers) and also in tim
 e (oscillatory and chaotic behaviors) (3). We thus are systematically clon
 ing and GFP expressing the putative genes involved in ion dynamics. Recent
 ly we cloned the first proton pump P-ATPase from tobacco pollen (Nt AHA- N
 icotiana H+ ATPase)\, which shows clear correlation with the flux patterns
 : NHA is excluded from the apex membrane by mechanisms involving polarized
  translation\, the actin cytoskeleton and membrane recycling (4). Nt AHA g
 ets polarized soon after hydration\, and its absence is predictive of the 
 germination pore. Information about fluxes and underlying molecular mechan
 isms are now being integrated in intracellular diffusion models which shou
 ld allow us to test the adequacy of our model. \n\n(1) Int.J.Dev.Biol. 49:
 595-614\, 2005\; Int.J.Dev.Biol. 49:615-632\, 2005\;\n(2) BioEssays\, 23:8
 6-94\, 2001 \n(3) Int.J.Dev.Biol.\, doi:10.1387/ijdb.072296em\, 2008\; Sex
 .Plant Reprod.\, doi:10.1007/s00497-008-0076-x\, 2008 \n(4) Plant Cell\, 2
 0:614-634\, 2008.\n\nhttp://www.igc.gulbenkian.pt/research/unit/38
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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