engleski

Characterisation of chloroplast thylakoid protein TROL in Arabidopsis thaliana

Poster abstract: The thylakoid membranes of chloroplasts convert light energy into a stable chemical energy of NADPH and ATP in an exceptional way. Although we are familiar with the proteins and multisubunit complexes that are involved in basic photosynthesis pathways, there are numerous proteins with still unknown functions. A large percentage of them are thylakoid membrane proteins. We are using reverse genetics approach to identify novel auxiliary thylakoid components that are included in signaling pathways in photosynthesis. Our current research is focused on elucidating the function of the thylakoid membrane protein TROL (Thylakoid Rhodanese-like) in plant Arabidopsis thaliana (L.) Heynh. Localization studies using C-terminal YFP fusion and in vitro chloroplast import assays confirmed its thylakoid localization and have demonstrated that TROL possesses characteristics of an integral membrane component. Furthermore, TROL is most likely exclusively located in non-apressed thylakoid regions. A strong interaction between TROL and FNR was demonstrated by co-immunoprecipitation experiments and yeast two hybrid methods, indicating that TROL could be one of the membrane docking sites for FNR. FNR catalyses the final electron transfer of oxygenic photosynthesis from ferredoxin to NAD(P). We were able to characterize a SAIL line with no production of TROL (knock-out plants) and to produce transgenic plants underexpressing TROL. Electron transport analysis clearly showed a significant difference between wild type and transgene photosynthetic rate. Knock-out and antisense lines had severely lowered relative electron transport rate (ETR) at light intensities exceeding 250 ?molPHOTONS m-2s-1. Simultaneously, the amount of nonphotochemical quenching (NPQ) increases, indicating enhanced dissipation of absorbed light energy as heat. This protein could also be interesting from the evolutionary point of view. TROL possesses rhodanese-like domain linked to a module which interacts with FNR. Rhodaneses are very old group of proteins, suggested to be involved in distinct biological functions such as cyanide detoxification, formation of prosthetic groups in iron-sulfur proteins and thiamin biosynthesis. It is presumed that all tyrosine-specific and dual-specifity phosphatases have evolved from a rhodanese-like precursor. Currently we are producing constructs for complementation of our knock-out line, hoping to create transgenic plants with modified protein TROL (for instance, a protein without rhodanese-like domain).

thylakoid proteins; signaling; rhodaneses

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