A1 Refereed original research article in a scientific journal
Over-production of the D1:2 protein makes Synechococcus cells more tolerant to photoinhibition of Photosystem II
Authors: Soitamo AJ, Zhou G, Clarke AK, Oquist G, Gustafsson P, Aro EM
Publisher: KLUWER ACADEMIC PUBL
Publication year: 1996
Journal:: Plant Molecular Biology
Journal name in source: PLANT MOLECULAR BIOLOGY
Journal acronym: PLANT MOL BIOL
Volume: 30
Issue: 3
First page : 467
Last page: 478
Number of pages: 12
ISSN: 0167-4412
DOI: https://doi.org/10.1007/BF00049325
Abstract
Over-expression of the psbAIII gene encoding for the D1 protein (form II; D1:2) of the photosystem II reaction centre in the Synechococcus sp. PCC 7942 was studied using a inc promoter and the lacI(Q) system. Over-expression was induced with 40 mu g/ml IPTG in the growth medium for either 6 or 12 h at growth irradiance (50 mu mol photons m(-2) s(-1)). This treatment doubled the amount of psbAII/III mRNA and the D1:2 protein in membranes but decreased the amount of psbAI messages and the D1:1 protein. The total amount of both heterodimeric reaction centre proteins, D1 and D2, remained constant under growth light conditions, indicating that the number of PSII centres in the membranes was not affected, only the form of the D1 protein was changed from D1:1 to D1:2 in most centres, When the cells were photoinhibited either at 500 or 1000 mu mol photons m(-2) s(-1), in the presence or absence of the protein synthesis inhibitor lincomycin, the D1:2 protein remained at a higher level in cells in which over-expression had been induced by IPTG. These cells were also less prone to photoinhibition of PSII. It is suggested that the tolerance of cells to photoinhibition increases when most PSII reaction centres contain the D1:2 protein at the beginning of high irradiance. This tolerance is further strengthened by maintaining psbAIII gene over-expression during the photoinhibitory treatment.
Over-expression of the psbAIII gene encoding for the D1 protein (form II; D1:2) of the photosystem II reaction centre in the Synechococcus sp. PCC 7942 was studied using a inc promoter and the lacI(Q) system. Over-expression was induced with 40 mu g/ml IPTG in the growth medium for either 6 or 12 h at growth irradiance (50 mu mol photons m(-2) s(-1)). This treatment doubled the amount of psbAII/III mRNA and the D1:2 protein in membranes but decreased the amount of psbAI messages and the D1:1 protein. The total amount of both heterodimeric reaction centre proteins, D1 and D2, remained constant under growth light conditions, indicating that the number of PSII centres in the membranes was not affected, only the form of the D1 protein was changed from D1:1 to D1:2 in most centres, When the cells were photoinhibited either at 500 or 1000 mu mol photons m(-2) s(-1), in the presence or absence of the protein synthesis inhibitor lincomycin, the D1:2 protein remained at a higher level in cells in which over-expression had been induced by IPTG. These cells were also less prone to photoinhibition of PSII. It is suggested that the tolerance of cells to photoinhibition increases when most PSII reaction centres contain the D1:2 protein at the beginning of high irradiance. This tolerance is further strengthened by maintaining psbAIII gene over-expression during the photoinhibitory treatment.
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