engleski

The role of the gene product At4g01050 in the regulation of photosynthesis in Arabidopsis thaliana (L.) Heynh.

Photosynthesis is a highly complex and versatile network of processes performed by multiprotein complexes associated with pigment molecules. Although the structure and role of nearly all subunits of the major thylakoid complexes are discovered, the large-scale proteomic approaches identified a great number of so-called auxiliary proteins with completely uninvestigated roles in photosynthesis. The gene At4g01050 codes for the novel thylakoid protein designated TROL (the Thylakoid Rhodanese Like protein). TROL is located almost exclusively in the non-appressed thylakoids, predicting to face the stroma with its C-terminus, encompassing the ITEP domain, and to expose the central part to the lumen, encompassing the RHO domain. The yeast two-hybrid and coimmunoprecipitation experiments univocally showed that ITEP interacts with the ferredoxin: NADP+ oxidoreductase (FNR). The plants depleted of TROL (the trol line) failed to maintain the linear electron transfer rates at the level of the wild-type when exposed to the high-light intensities. In addition, the non-photochemical quenching (NPQ) in trol plants was significantly higher than in the wild-type, possibly revealing the function of TROL in plants exposed to high-light stress. The RHO domain shares the rhodanese-like three dimensional fold with the regulatory domains from the Cdc25 phosphatases. Functional rhodanese domains have a cysteine residue in the active-site, which enables them to participate in sulphur metabolism, while the RHO domain contains an aspartic acid residue instead of the cysteine. To question the possible role of RHO in the signalling across the chloroplast and towards the nucleus (the retrograde signalling), the trol plants were complemented with the modified versions of the TROL protein. The isolation of the multiprotein complexes in their native state from the thylakoid membranes revealed that TROL is assembled in three complexes, at 420 kDa, 190 kDa, and 120 kDa, respectively. The mass spectrometry analysis of the TROL-containing complexes identified a few possible interacting candidates. The ongoing research on these proteins and on complemented trol lines would help to untangle the perplexed network of signalling pathways in plant cells.

FNR; high-light; linear electron flow; retrograde signalling; rhodaneses

nije evidentirano