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Antisense inhibition of the photosynthetic antenna proteins CP29 and CP26: implications for the mechanism of protective energy dissipation
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).ORCID-id: 0000-0002-7906-6891
2001 (Engelska)Ingår i: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 13, nr 5, s. 1193-1204Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The specific roles of the chlorophyll a/b binding proteins CP29 and CP26 in light harvesting and energy dissipation within the photosynthetic apparatus have been investigated. Arabidopsis was transformed with antisense constructs against the genes encoding the CP29 or CP26 apoprotein, which gave rise to several transgenic lines with remarkably low amounts of the antisense target proteins. The decrease in the level of CP24 protein in the CP29 antisense lines indicates a physical interaction between these complexes. Analysis of chlorophyll fluorescence showed that removal of the proteins affected photosystem II function, probably as a result of changes in the organization of the light-harvesting antenna. However, whole plant measurements showed that overall photosynthetic rates were similar to those in the wild type. Both antisense lines were capable of the qE type of nonphotochemical fluorescence quenching, although there were minor changes in the capacity for quenching and in its induction kinetics. High-light-induced violaxanthin deepoxidation to zeaxanthin was not affected, although the pool size of these pigments was decreased slightly. We conclude that CP29 and CP26 are unlikely to be sites for nonphotochemical quenching.

Ort, förlag, år, upplaga, sidor
American Society of Plant Biologists , 2001. Vol. 13, nr 5, s. 1193-1204
Forskningsämne
fysiologisk botanik
Identifikatorer
URN: urn:nbn:se:umu:diva-3907DOI: 10.1105/tpc.13.5.1193ISI: 000169030000017OAI: oai:DiVA.org:umu-3907DiVA, id: diva2:142811
Tillgänglig från: 2003-02-28 Skapad: 2003-02-28 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Ingår i avhandling
1. Dissecting the photosystem II light-harvesting antenna
Öppna denna publikation i ny flik eller fönster >>Dissecting the photosystem II light-harvesting antenna
2003 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

In photosynthesis, sunlight is converted into chemical energy that is stored mainly as carbohydrates and supplies basically all life on Earth with energy.

In order to efficiently absorb the light energy, plants have developed the outer light harvesting antenna, which is composed of ten different protein subunits (LHC) that bind chlorophyll a and b as well as different carotenoids. In addition to the light harvesting function, the antenna has the capacity to dissipate excess energy as heat (feedback de-excitation or qE), which is crucial to avoid oxidative damage under conditions of high excitation pressure. Another regulatory function in the antenna is the state transitions in which the distribution of the trimeric LHC II between photosystem I (PS I) and II is controlled. The same ten antenna proteins are conserved in all higher plants and based on evolutionary arguments this has led to the suggestion that each protein has a specific function.

I have investigated the functions of individual antenna proteins of PS II (Lhcb proteins) by antisense inhibition in the model plant Arabidopsis thaliana. Four antisense lines were obtained, in which the target proteins were reduced, in some cases beyond detection level, in other cases small amounts remained.

The results show that CP29 has a unique function as organising the antenna. CP26 can form trimers that substitute for Lhcb1 and Lhcb2 in the antenna structure, but the trimers that accumulate as a response to the lack of Lhcb1 and Lhcb2 cannot take over the LHC II function in state transitions. It has been argued that LHC II is essential for grana stacking, but antisense plants without Lhcb1 and Lhcb2 do form grana. Furthermore, LHC II is necessary to maintain growth rates in very low light.

Numerous biochemical evidences have suggested that CP29 and/or CP26 were crucial for feedback de-excitation. Analysis of two antisense lines each lacking one of these proteins clearly shows that there is no direct involvement of either CP29 or CP26 in this process. Investigation of the other antisense lines shows that no Lhcb protein is indispensable for qE. A model for feedback de-excitation is presented in which PsbS plays a major role.

The positions of the minor antenna proteins in the PS II supercomplex were established by comparisons of transmission electron micrographs of supercomplexes from the wild type and antisense plants.

A fitness experiment was conducted where the antisense plants were grown in the field and seed production was used to estimate the fitness of the different genotypes. Based on the results from this experiment it is concluded that each Lhcb protein is important, because all antisense lines show reduced fitness in the field.

Ort, förlag, år, upplaga, sidor
Umeå: Fysiologisk botanik, 2003. s. 59
Nyckelord
Plant physiology, antisense, Arabidopsis thaliana, chlorophyll, carotenoid, feedback de-excitation, fitness, LHC, NPQ, photosynthesis, state transitions, xanthophyll, Växtfysiologi
Nationell ämneskategori
Botanik
Forskningsämne
fysiologisk botanik
Identifikatorer
urn:nbn:se:umu:diva-25 (URN)91-7305-387-2 (ISBN)
Disputation
2003-02-28, Umeå, 10:00
Tillgänglig från: 2003-02-28 Skapad: 2003-02-28 Senast uppdaterad: 2012-08-08Bibliografiskt granskad

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Jansson, Stefan

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