engleski

Unraveling the role of dually localized protein TROL at the inner envelope of chloroplasts

TROL (Thylakoid rhodanase-like protein) has been discovered in the proximity of photosynthetic apparatus of higher plants and is a key component for the regulation of post-photosynthetic electron transfer. At the end of the photosynthetic electron chain, at the stromal side of photosystem I (PSI), TROL docks and dynamically interacts with FNR (ferredoxin:NADPH oxydoreductase), bringing it into the vicinity of PSI and electron donor ferredoxin (Fd). Electrons are handed over from Fd to FNR and preferentially further to the Calvin cycle in the form of reduced NADP+. In the absence of TROL linear electron flow is impaired, while the distribution of high-energy electrons is directed towards the ROS detoxification pathways rather than to the NADP+ reduction. Trol plants show increased stress resistance along with significantly enhanced ROS detoxification and are therefore potential candidates for more resilient plants of the world with constantly increasing environmental stresses. TROL is localized in the inner envelope (IE) of chloroplasts as a precursor of 70 kDa, where its function is so far unknown, and in the thylakoids as a 66 kDa mature form, where it participates at the regulation of photosynthetic electron utilization. By presequence directed mutagenesis we altered the presequence processing site of TROL precursor protein and by using in vitro protein import experiments we managed to arrest TROL at a single location – in the IE membrane. Furthermore, we engineered Arabidopsis plants containing TROL protein just in the IE. Such plants might further reveal its roles in regulation of photosynthesis as well as its yet unknown function in the inner envelope. At this point we attempt, at the level of the IE membrane, to resolve whether TROL represents just a storage protein for FNR or is involved in redox sensing and/or in protein import.

TROL ; FNR ; photosynthesis ; electron transfer ; dual localization ; inner envelope

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