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Signal derived from photosynthic electron transport regulates the expression of methionine sulfoxide reductase (Msr) gene in the green macroalga Ulva fasciata DelileHsu, Yuan-ting 20 November 2008 (has links)
This study has investigated the involvement of photosynthetic electron transport chain on the regulation of gene expression of methionine sulfoxide reductase (UfMSR) in the marine macroalga Ulva fasciata Delile.UfMSRA is from copper stress and UfMSRB ir from hypersalinity stress. UfMSRA is similar to Arabidopsis AtMSRA4 and UfMSRB is similar to AtMSRB1. UfMSRA is specific to the MetSO S-enantiomer and UfMSRB catalytically reduces the MetSO R-enantiomer. Both enzymes are required, since in the cell oxidation of Met residues at the sulfur atom results in a racemic mixture of the two stereoisomers. UfMSRA and UfMSRB transcripts were increased by white light, blue light and red light with the maximum at 1 h following a decline, but kept constant in the dark. The magnitude of UfMSRA and UfMSRB transcript increase showed a positive linear correlation to increasing light intensity from 0-1200 u mole¡Pm-2¡Ps-1. The treatment with linear electron transport
chain inhibitors, hydroxylamine, 3-(3,4-dichlorophenyl) -1,1-dimethylurea (DCMU),
2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) and stigmatellin,
effectively inhibited PS II activity under 300 u mole¡Pm-2¡Ps-1 irradiance. DBMIB and
stigmatellin can increase UfMSRA transcript that was reversed by
2,6-dichlorophenolindophenol (DCPIP), a PS I electron donor. It indicates that the
block of electron transport of the downstream of cytochrome b6f indeuces UfMSRA
gene expression. Hydroxylamine, DCMU and DBMIB decreased UfMSRB transcript
that was not reversed by DCPIP while stigmatellin increased UfMSRB mRNA level,
reflecting a role of reduced state with Qo site located at cytochrome b6f on the
induction of UfMSRB gene expression. The cyclic electron transport chain inhibitors,
antimycin A that inhibited photosynthetic electron transport, can inhibit the increase
of UfMSRA and UfMSRB transcripts by irradiance. UfMSRA and UfMSRB gene
expression were both modulated by cyclic electron transport chain and linear electron
transport chain. These results reveal that photosynthetic electron transport chain
modulates UfMSRA and UfMSRB gene expression by change its redox state.
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Photosynthetic electron transport modulates genes expression of Methionine Sulfoxide Reductase (MSR) in Chlamydomonas reinhardtiiShie, Shu-Chiu 25 July 2011 (has links)
Chlamydomonas reinhardtii can utilize CO2 for autotrophic growth (HSM plus
5% CO2) or acetate for mixotrophic growth (TAP). This study was to elucidate the
differential regulation of methionine sulfoxide reductase (MSR) gene expression
between HSM plus 5% CO2 and TAP cultured cells, and also to determine the
difference of gene expression in response to high light (1,000 £gE m-2 s-1). The role of
photosynthetic electron transport (PET) in the regulation of MSR gene expression was
also examined by the use of PET inhibitors. High light inhibited PSII activity (Fv/Fm
and Fv'/Fm') of HSM plus 5% CO2 and TAP cultured cells., while the responses of
CrMSR gene expression in mixotrophically grown cells were different from
autotrophically grown cells, High light increased the expression of CrMSRA1,
CrMSRA2, CrMSRA3, CrMSRA5, CrMSRB1.2, and CrMSRB2.1, but inhibited the
expression of CrMSRA4 and CrMSRB2.2 in autotrophically grown cells. The
expression of CrMSRA3, CrMSRA5, and CrMSRB2.1 in mixotrophically grown cells
was increased by high light but that of CrMSRA1, CrMSRA4, and CrMSRB2.2 was
inhbited. The number of MSR isoform that was up-regulated by high light was greater
in autotrophically grown cell than that in mixotrophically grown cells. Using the PET
inhibitors (3-(3,4-dichlorophenyl)-1,1- dimethylurea (DCMU) and
2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB)), most of the CrMSRA
expression was regulated by reduced QA for autotrophically grown cells while
reduced PQ was the main site for mixotrophically grown cells by high light. The
expression of CrMSRB in autotrophically grown cells was mainy modulated by QA (-)
or Cytb6f (-), while that was not affected by PET, except a role of Cytb6f (-) on the
high light-induced CrMSRB2.2 expression. We fouind that CrMSRB gene expression
in autotrophically grown cells was highly affected by PET but not for micotrophically
grtown cells. The present result that H2O2 did not accumulate in autotrophically and
mixotrophically grown cells suggests that H2O2 may be not involved in the regulation
of high light regulation of CrMSR gene expression. The present study shows that the
mRNA expression of CrMSR isoforms in Chlamydomonas was diffrerentially
regulated between autotrophically and mixttrophically grown cells. The relationship
between the utilization of different C source and CrMSR gene expression will be
discussed.
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Involvement of the chloroplastic photosynthetically electron transport in the differential expression of nuclear genes Methionine Sulfoxide Reductase (MSR) isoforms by excess light in Chlamydomonas reinhardtiiTseng, Yu-Lu 28 June 2011 (has links)
Methionine sulfoxide reductase A (MSRA) and MSRB are responsible for the repairing of methionine-R-sulfoxide (Met-S-SO) and methionine-S-sulfoxide (Met-R-SO) back to me-thionine, respectively. Five MSRA isoforms and four MSRB isoforms are discovered in the unicellular green alga Chlamydomonas reinhardtii. Whether high light regulates CrMSR ex-pression via photosynthetic electron transport (PET) was examined. By checking the se-quence of PCR product of each isoform, quantitative real-time primers were designed for discrimination of isoform expression. Light ≥ 300 £gE m-2 s-1 and PET inhibitors inhibited PSII activity (Fv/Fm, Fv´/Fm´) and photosynthetic O2 evolution rate, particularly 1,000 £gE m-2 s-1, in which it did not recover after 3 h. A transfer to dark decreased CrMSRA2, CrMSRA3, CrMSRB1.1, CrMSRB1.2, CrMSRB2.1 mRNA levels but increased CrMSRA4 mRNA levels. When exposed to 50, 300, 600, or 1,000 £gE m-2 s-1, CrMSRA2, CrMSRA3, CrMSRA5, CrMSRB1.1, CrMSRB2.1 and CrMSRB2.2 mRNA levels increased as light ≥ 300 £gE m-2 s-1, and concomitantly CrMSRA4 mRNA level decreased. Changes in mRNA levels increased as light intensity increased. The treatment of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) in 1,000 £gE m-2 s-1 inhibited high light effect, and the treatment of 2,5-dibromo-3-methyl-6- isopropyl-p- benzoquinone (DBMIB) in 50 £gE m-2 s-1 increased CrMSRA3, CrMSRA5 and CrMSRB2.2 mRNA levels but decreased CrMSRA4 mRNA level. The application of phena-zine methosulfate (PMS), an electron donor to P700+ that promotes cyclic electron transport, in 300 £gE m-2 s-1 enhanced the increase of CrMSRA3 and CrMSRA5 mRNA levels by high light but inhibited the decrease of CrMSRA4 mRNA level, reflecting a role of cyclic PET. The above results let us to draw a conclusion that plastoquinone as reduced status mediates the expression of CrMSRA3, CrMSRA4, CrMSRA5 and CrMSRB2.2 by high light. The im-plication of linear electron transport and cyclic electron transport on the regulation of CrMSR gene expression will be discussed.We speculated that the high light up-regulation of CrMSR mRNA expression offers the resistance of Chlamydomonas to photooxidative stress.
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