engleski

TLP40 is involved in state II transitions

Photosynthesis represents the crucial biochemical process responsible for the production of oxygen and food, and is carried out in two phases: a light and a dark phase. Chloroplasts, organelles in plant cells are responsible for photosynthesis. Chloroplast protein TLP40 (thylakoid lumen PPIase of 40 kDa), cychlophilin-like PPIase located in thylakoid lumen, was found to be involved in protein folding, biogenesis, and intraorganelle signaling. TLP40 shows peptidyl-prolyl cis-trans isomerase protein folding activity characteristic of immunophilins and was co-isolated with thylakoid membrane phosphatase from spinach. Gene coding CYP38 protein, ortholog of TLP40 from spinach, is located on the 3rd chromosome of Arabidopsis thaliana. To characterize the function of this protein in vivo, we analyzed knock-out Arabidopsis thaliana lines: cyp38-N and cyp38-M, which were screened for T-DNA insertion. Gene was interrupted by T-DNA insertion at position 1962 (6th exon) in cyp38-M, as confirmed by PCR and tested by Western blotting. Chlorophyll fluorescence measured in vivo with MINI-PAM portable chlorophyll fluorometer (Waltz) indicated slightly elevated non-photochemical quenching (NPQ) and considerably lowered relative electron transport rate (ETR) of mutants compared to wild-type plants. Also, PSII efficiency measured (Fv/Fm ratio), under normal light conditions was decreased in mutants. Analysis of chloroplast ultrastructure between CYP38 deficient and wild-type plants was performed, but no marked differences were observed. A quantitative state-transition measurements of intact rosetta leaves revealed that CYP38 gene inactivation leads to impaired state II transition implicating possible defects of antenna dephosphorylation in mutants lacking CYP38 protein.

Arabidopsis; immunophilin; photosynthesis; PSII; phosphorylation; state-transitions

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