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@ARTICLE{GarcaPlazaola:56789,
      author       = {García-Plazaola, J. I. and Matsubara, S. and Osmond, C.
                      B.},
      title        = {{T}he lutein epoxide cycle in higher plants: its
                      relationships to other xanthophyll cycles and possible
                      functions},
      journal      = {Functional plant biology},
      volume       = {34},
      issn         = {1445-4408},
      address      = {Collingwood, Victoria},
      publisher    = {CSIRO Publ.},
      reportid     = {PreJuSER-56789},
      pages        = {759 - 773},
      year         = {2007},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {Several xanthophyll cycles have been described in
                      photosynthetic organisms. Among them, only two are present
                      in higher plants: the ubiquitous violaxanthin (V) cycle, and
                      the taxonomically restricted lutein epoxide (Lx) cycle,
                      whereas four cycles seem to occur in algae. Although V is
                      synthesised through the beta-branch of the carotenoid
                      biosynthetic pathway and Lx is the product of the
                      alpha-branch; both are co-located in the same sites of the
                      photosynthetic pigment- protein complexes isolated from
                      thylakoids. Both xanthophylls are also de-epoxidised upon
                      light exposure by the same enzyme, violaxanthin de-epoxidase
                      (VDE) leading to the formation of zeaxanthin (Z) and lutein
                      (L) at comparable rates. In contrast with VDE, the reverse
                      reaction presumably catalysed by zeaxanthin epoxidase (ZE),
                      is much slower (or even inactive) with L than with
                      antheraxanthin (A) or Z. Consequently many species lack Lx
                      altogether, and although the presence of Lx shows an
                      irregular taxonomical distribution in unrelated taxa, it has
                      a high fidelity at family level. In those plants which
                      accumulate Lx, variations in ZE activity in vivo mean that a
                      complete Lx-cycle occurs in some (with Lx pools being
                      restored overnight), whereas in others a truncated cycle is
                      observed in which VDE converts Lx into L, but regeneration
                      of Lx by ZE is extremely slow. Accumulation of Lx to high
                      concentrations is found most commonly in old leaves in
                      deeply shaded canopies, and the Lx cycle in these leaves is
                      usually truncated. This seemingly anomalous situation
                      presumably arises because ZE has a low but finite affinity
                      for L, and because deeply shaded leaves are not often
                      exposed to light intensities strong enough to activate VDE.
                      Notably, both in vitro and in vivo studies have recently
                      shown that accumulation of Lx can increase the light
                      harvesting efficiency in the antennae of PSII. We propose a
                      model for the truncated Lx cycle in strong light in which
                      VDE converts Lx to L which then occupies sites L2 and V1 in
                      the light-harvesting antenna complex of PSII (Lhcb),
                      displacing V and Z. There is correlative evidence that this
                      photoconverted L facilitates energy dissipation via
                      non-photochemical quenching and thereby converts a highly
                      efficient light harvesting system to an energy dissipating
                      system with improved capacity to engage photoprotection.
                      Operation of the alpha- and beta- xanthophyll cycles with
                      different L and Z epoxidation kinetics thus allows a
                      combination of rapidly and slowly reversible modulation of
                      light harvesting and photoprotection, with each cycle having
                      distinct effects. Based on the patchy taxonomical
                      distribution of Lx, we propose that the presence of Lx (and
                      the Lx cycle) could be the result of a recurrent mutation in
                      the epoxidase gene that increases its affinity for L, which
                      is conserved whenever it confers an evolutionary advantage.},
      keywords     = {J (WoSType)},
      cin          = {ICG-3},
      ddc          = {580},
      cid          = {I:(DE-Juel1)ICG-3-20090406},
      pnm          = {Terrestrische Umwelt},
      pid          = {G:(DE-Juel1)FUEK407},
      shelfmark    = {Plant Sciences},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000249104100001},
      doi          = {10.1071/FP07095},
      url          = {https://juser.fz-juelich.de/record/56789},
}