The roles of specific xanthophylls in light utilization |
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Authors: | Ljudmila Kalituho Jennifer Rech Peter Jahns |
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Institution: | 1.Institute of Plant Biochemistry,Heinrich-Heine-University Düsseldorf,Dusseldorf,Germany |
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Abstract: | To evaluate the role of specific xanthophylls in light utilization, wild-type and xanthophyll mutant plants (npq1, npq2, lut2, lut2npq1 and lut2npq2) from Arabidopsis thaliana were grown under three different light regimes: 30 (low light, LL), 150 (medium light, ML) and 450 (high light, HL) μmol
photons m−2 s−1. We studied the pigment content, growth rate, xanthophyll cycle activity, chlorophyll fluorescence parameters and the response
to photoinhibition. All genotypes differed strongly in the growth rates and the resistance against photoinhibition. In particular,
replacement of lutein (Lut) by violaxanthin (Vx) in the lut2npq1 mutant did not affect the growth at non-saturating light intensities (LL and ML), but led to a pronounced reduction of growth
under HL conditions, indicating an important photoprotective role of Lut. This was further supported by a much higher sensitivity
of all Lut-deficient plants to photoinhibition in comparison with the wild type. In contrast, replacement of Lut by zeaxanthin
(Zx) in lut2npq2 led to a pronounced reduction of growth under all light regimes, most likely related to the permanent non-photochemical dissipation
of excitation energy by Zx at Vx-binding sites and the destabilization of antenna proteins by binding of Zx to Lut-binding
sites. The high susceptibility of lut2npq2 to photoinhibition in comparison with npq2 further indicated that the photoprotective function of Zx is abolished in the absence of Lut. Thus, it can be concluded from
our work that neither Vx nor Zx is able to fulfil the essential photoprotective function at Lut-binding sites under in vivo
conditions. |
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Keywords: | Antenna proteins Arabidopsis Carotenoids Light utilization Photoprotection Xanthophyll cycle |
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