Susanti, Novita I.
The role of arabidopsis UV-resistance locus 8 protein in regulating photosynthetic competence.
MSc(R) thesis, University of Glasgow.
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Arabidopsis thaliana UV-Resistance Locus 8 (UVR8) is a UV-B-specific protein that regulates genes concerned with protection against ultraviolet-B (UV-B) radiation. Some of these genes encode chloroplast proteins including the RNA polymerase sigma factor, sigma 5 (SIG5) and one of the Early Light Induced Proteins in Arabidopsis thaliana (ELIP1). According to this discovery, UVR8 had been proposed to be involved in regulating chloroplast related genes that encode Photosystem II Reaction Center core proteins, the D1 and D2 proteins. This hypothesis was examined in this study. Several physiological approaches and measurements of transcripts and protein were done using uvr8-1, sig5.1, sig5-2 and elip1/2 mutants. This study showed that the uvr8-1 mutant is very sensitive to UV-B compared to wild type and other mutants and uvr8-1 had a reduction of its photosynthetic efficiency (measured as Fv/Fm values). Assessments of SIG5 and ELIP1 transcripts and measurements of photosynthetic efficiency showed that these genes are not essential in UV-B protection. Further, transcript measurements of psbA and psbD-BLRP, which encode the D1 and D2 protein respectively, showed that UVR8 is involved in accumulation of psbD-BLRP transcripts but little affected psbA transcripts. Moreover, UV-B caused reduction of D1 protein consistent with the reduction of the Fv/Fm values when wild type and uvr8-1 plants were exposed to UVB, but the role of UVR8 in this mechanism needs to be investigated further. However, the effect of UV-B on D2 protein still remains unclear.
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