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SUMMARY:Biogenesis and regulation of the photosynthetic apparatus - Profes
 sor Jean-David Rochaix\, University of Geneva
DTSTART:20071011T150000Z
DTEND:20071011T160000Z
UID:TALK8075@talks.cam.ac.uk
CONTACT:3901
DESCRIPTION:The biogenesis of the photosynthetic apparatus of algae and la
 nd plants depends on the concerted interactions of the nuclear and chlorop
 last genetic systems. A large number of nucleus-encoded factors are involv
 ed in post-transcriptional steps of chloroplast gene expression including 
 RNA processing and splicing\, translation and assembly of the photosynthet
 ic complexes. One example is provided by the translation factor Tab2/ATAB2
  which is conserved in oxygenic photosynthetic organisms. Considering its 
 role in protein synthesis and its photoreceptor-mediated expression\, ATAB
 2 represents a novel factor in the signalling pathway of light-controlled 
 translation of photosystem proteins during early plant development. Photos
 ynthetic organisms are able to adjust to changes in light quality and to m
 aintain a high photosynthetic yield and energy homeostasis through state t
 ransitions. This process involves a reorganization of the light-harvesting
  system (LHCII) in the thylakoid membranes and the balancing of light exci
 tation energy between PSII and PSI. Excess stimulation of PSII relative to
  PSI leads to the reduction of the plastoquinone pool and to the activatio
 n of a kinase\, to the phosphorylation of LHCII and to the displacement of
  LHCII from PSII to PSI (state 2). Excess stimulation of PSI leads to the 
 reverse process (state 1). We have used a genetic approach in Chlamydomona
 s with the ultimate aim of identifying some of the key components involved
  in the signaling chain of state transitions. In this way the thylakoid-as
 sociated Ser-Thr kinase Stt7 was identified which is required for the phos
 phorylation of LHCII and for state transitions. It belongs to a small fami
 ly of protein kinases\, also conserved in land plants\, which are part of 
 a regulatory circuitry apparently involved both in short term and long ter
 m acclimation.\nhttp://www.molbio.unige.ch/rochaix/index.php
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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