engleski

CYP38 auxiliary enzyme in Arabidopsis thaliana is involved in state II transitions

D1 protein of the PSII reaction center mainly segregated in stacked membrane layers is prone to photo-oxidative damage. After being removed from PSII, D1 is migrated to the unstacked membrane domain for repair. Among auxiliary enzymes, chloroplast immunophilin protein SoTLP40 (thylakoid lumen PPIase of 40 kDa) co-isolated with thylakoid membrane phosphatase from spinach was found to be involved in the biogenesis and maintenance of PSII. Lumenal immunophilin protein AtCYP38 (cyclophilin 38 kDa) ortholog of SoTLP40, also was suggested to play a role in the PSII repair and assembly. In this work we used reverse genetics approach and were focused on functional aspects of the gene At3g01480 coding CYP38 protein (A. thaliana). Analyzed knock-out A. thaliana line cyp38-2 was screened for T-DNA insertion as confirmed by PCR and tested by Western blotting. Functional characterization of CYP38 protein included antisense-mediated gene silencing (asCYP38) using Gateway technology and floral dip method. Chloroplast and thylakoid membrane system were analyzed in mesophyll cells of cyp38-1, cyp38-2, asCYP38 and wild-type (wt) Arabidopsis leaves using electron microscopy, while chlorophyll a fluorescence transient measured in CYP38 deficient plants in vivo indicated reduced photosynthetic performance as a consequence of conformational changes in PSII. Quantitative state-transition measurements of CYP38 mutant and wt plants indicated that CYP38 gene inactivation leads to impaired state II transition implicating possible defects of antenna dephosphorylation in mutants lacking CYP38 protein. Thus, CYP38 points towards dynamic interaction with thylakoid-associated phosphatase TAP38 in order to trigger accelerated repair of photodamaged PSII protein D1.

photosynthesis; CYP38; D1; state-transitions

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