engleski

Unexpected links connecting photosynthesis with plant stress responses

Background and aims Although major components of plant photosynthetic apparatus chain are known, the knowledge about fine tuning of energy transduction within the chloroplasts is quite limited. Apart from recently discovered protein TROL, necessary for the binding of ferredoxin-NADP+:oxidoreductase (FNR), we were able to identify further components which might form supramolecular structures necessary for maintaining thylakoid redox poise, repair of photosynthetic complexes, and plastid-to-nucleus signaling. Methods Thylakoid supramolecular protein complexes were resolved by using blue-native PAGE and probed with an anti-TROL antibody. Individual bands were subjected to mass spectroscopy analyses (MS). mRNA coexpression analyses were performed by using A. thaliana Co-Response database (AthCoR@CSB.DB). Arabidopsis plants with inactivated genes of interest were analyzed for phenotype, photosynthetic parameters, and changes of global gene expression. Key results Immunoblot analyses indicated that TROL could be found in the three major complexes, at 110, 120 and 420 kDa. The 420 kDa complex might contain representative subunits of cytochrome b6/f, PSI and PSII. TROL associated with FNR could be found in probably transient complex at about 190 kDa. MS analysis revealed that TROL might form a complex with the homologue of FtsH metaloprotease, theVAR2 protein. Co-expression analysis indicated that the gene At4g01150 has highly similar expression pattern to TROL. At4g01150 encodes a chloroplast paralog of PSI-P and shares 89.3% sequence identity with salt tolerance response protein ST6-40. Plants with a T-DNA insertion in At4g01150 accumulate reduced levels of TROL protein, implying their functional linkage. Conclusions Auxiliary proteins of thylakoid membranes play important roles in fine-tuning of photosynthesis. Apart from being responsible for the FNR binding, TROL might be involved in biogenesis of photosynthetic protein complexes via its interaction with the VAR2. Inactivation of TROL leads to increased stress tolerance of Arabidopsis plants. At4g01150 is stress-associated protein which can be functionally linked to TROL. Further association with CYP38 immunofilin is also possible.

ferredoxin-NADP+:oxidoreductase (FNR); TROL; linear photosynthetic flow; CYP38 immunofilin

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