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SUMMARY:Towards understanding of photoacclimation in algal photosynthesis 
 – regulation via redox and Ca2+ - Michael Hippler\, University of Munste
 r
DTSTART:20171214T130000Z
DTEND:20171214T140000Z
UID:TALK82491@talks.cam.ac.uk
CONTACT:david baulcombe
DESCRIPTION:Photosynthetic organisms must acclimate to their light environ
 ment to optimize photosynthesis and minimize photo-oxidative damage. In pl
 ants\, qE\, a component of non-photochemical quenching (NPQ)\, is required
  for thermal dissipation of excess absorbed light energy. In C. reinhardti
 i\, LHCSR3 was shown to be crucial for functional qE (Peers et al\, 2009).
  Increased cyclic electron flow (CEF) around PS I is known to promote qE i
 nduction by formation of a trans-thylakoid proton gradient. Functional CEF
  depends on a reorganization of the major protein complexes in the thylako
 id membrane\, leading to the formation of a PS I-cytochrome b6f supercompl
 ex (CEF-supercomplex) (Iwai et al\, 2010\; Terashima et al\, 2012). There 
 is evidence that that the chloroplast localized Ca2+ sensor protein (CAS) 
 is crucial for effective photo-acclimation in C. reinhardtii by controllin
 g the expression of LHCSR3 (Petroutsos et al\, 2011) and required for expr
 ession of proteins essential for the carbon-concentrating mechanism (CCM) 
 (Wang et al\, 2016). Moreover CAS and Ca2+ are involved in regulation of C
 EF. Ca2+-dependent regulation of CEF was shown via a combined function of 
 ANR1 and CAS\, associated with each other in the CEF-supercomplex (Terashi
 ma et al\, 2012). Further evidence for the importance of Ca2+ in the regul
 ation of photosynthesis is given by the identification (Hohner et al\, 201
 3) and characterization of a C. reinhardtii protein\, which combines four 
 EF-hands and a thioredoxin domain\, designated as calredoxin (CRX). Functi
 onal data demonstrate that recombinant CRX possesses Ca2+-dependent thiore
 doxin activity\, thereby linking Ca2+ with redox regulation (Hochmal et al
 \, 2016). Down-regulation of calredoxin expression resulted in increased C
 EF\, high ROS and elevated conductivity of the ATPase as well as in a stro
 ng repression of highlight-induced proteins\, including CCM-induced protei
 ns\, a phenotype similar to a CAS-deficient mutant\, suggesting a link bet
 ween CAS and CRX. \n\nReferences \n\nHochmal AK\, Zinzius K\, Charoenwatta
 nasatien R\, Gabelein P\, Mutoh R\, Tanaka H\, Schulze S\, Liu G\, Scholz 
 M\, Nordhues A\, Offenborn JN\, Petroutsos D\, Finazzi G\, Fufezan C\, Hua
 ng K\, Kurisu G\, Hippler M (2016) Calredoxin represents a novel type of c
 alcium-dependent sensor-responder connected to redox regulation in the chl
 oroplast. Nat Commun 7: 11847\n\nHohner R\, Barth J\, Magneschi L\, Jaeger
  D\, Niehues A\, Bald T\, Grossman A\, Fufezan C\, Hippler M (2013) The me
 tabolic status drives acclimation of iron deficiency responses in Chlamydo
 monas reinhardtii as revealed by proteomics based hierarchical clustering 
 and reverse genetics. Molecular & cellular proteomics : MCP 12: 2774-2790\
 n\nIwai M\, Takizawa K\, Tokutsu R\, Okamuro A\, Takahashi Y\, Minagawa J 
 (2010) Isolation of the elusive supercomplex that drives cyclic electron f
 low in photosynthesis. Nature 464: 1210-1213\n\nPeers G\, Truong TB\, Oste
 ndorf E\, Busch A\, Elrad D\, Grossman AR\, Hippler M\, Niyogi KK (2009) A
 n ancient light-harvesting protein is critical for the regulation of algal
  photosynthesis. Nature 462: 518-521\n\nPetroutsos D\, Busch A\, Janssen I
 \, Trompelt K\, Bergner SV\, Weinl S\, Holtkamp M\, Karst U\, Kudla J\, Hi
 ppler M (2011) The chloroplast calcium sensor CAS is required for photoacc
 limation in Chlamydomonas reinhardtii. The Plant cell 23: 2950-2963\n\nTer
 ashima M\, Petroutsos D\, Hudig M\, Tolstygina I\, Trompelt K\, Gabelein P
 \, Fufezan C\, Kudla J\, Weinl S\, Finazzi G\, Hippler M (2012) Calcium-de
 pendent regulation of cyclic photosynthetic electron transfer by a CAS\, A
 NR1\, and PGRL1 complex. Proceedings of the National Academy of Sciences o
 f the United States of America 109: 17717-17722\n\nWang L\, Yamano T\, Tak
 ane S\, Niikawa Y\, Toyokawa C\, Ozawa SI\, Tokutsu R\, Takahashi Y\, Mina
 gawa J\, Kanesaki Y\, Yoshikawa H\, Fukuzawa H (2016) Chloroplast-mediated
  regulation of CO2-concentrating mechanism by Ca2+-binding protein CAS in 
 the green alga Chlamydomonas reinhardtii. Proceedings of the National Acad
 emy of Sciences of the United States of America 113: 12586-12591\n\n
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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