Functions of the water soluble chlorophyll-binding protein in plants |
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Authors: | Damaraju Sridevi Schlede Stephanie Eckhardt Ulrich Lokstein Heiko Grimm Bernhard |
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Affiliation: | a Institut für Biologie/Pflanzenphysiologie, Humboldt-Universität zu Berlin, Philippstr. 13, Gebäude 12, D-10115 Berlin, Germany b Institut für Biochemie und Biologie/Pflanzenphysiologie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, Haus 20, D-14476 Potsdam-Golm, Germany |
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Abstract: | Functional aspects of water soluble chlorophyll-binding protein (WSCP) in plants were investigated during the courses of leaf senescence, chlorophyll biogenesis, stress response and photoprotection. The cDNA sequence encoding WSCP from cauliflower was cloned into a binary vector to facilitate Agrobacterium tumefaciens mediated transformation of Nicotiana tabacum. The resultant transgenic tobacco plants overexpressed the CauWSCP gene under the control of a 35S-promoter. Analyses of protein and pigment contents indicate that WSCP overexpression does not enhance chlorophyll catabolism in vivo, thus rendering a role of WSCP in Chl degradation unlikely. Accumulation of higher levels of protochlorophyllide in WSCP overexpressor plants corroborates a proposed temporary storage and carrier function of WSCP for chlorophyll and late precursors. Although WSCP overexpressor plants did not show significant differences in non-photochemical quenching of chlorophyll fluorescence, they are characterized by significantly lower zeaxanthin accumulation and peroxidase activity at different light intensities, even at high light intensities of 700-900 μmol photons m−2 s−1. These results suggest a photoprotective function of the functional chlorophyll binding-WSCP tetramer by shielding of chlorophylls from molecular oxygen. |
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Keywords: | AA, amino acids AL, actinic light ALA, 5-aminolevulinic acid Ax, antheraxanthin BChl, bacteriochlorophyll Chl, chlorophyll Chlase, chlorophyllase Chlide, chlorophyllide DAB, 3,3&prime -diaminobenzidine NPQ, non-photochemical quenching of Chl fluorescence PChlide, protochlorophyllide PSI, II, photosystems I and II ROS, reactive oxygen species Vx, violaxanthin WSCP, water soluble chlorophyll-binding protein Zx, zeaxanthin |
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