The psbA gene family responds differentially to light and UVB stress in Gloeobacter violaceus PCC 7421, a deeply divergent cyanobacterium.
نویسندگان
چکیده
Gloeobacter violaceus PCC 7421 is a slow-growing cyanobacterium which lacks thylakoid membranes, but whose five-membered psbA gene family encodes three isoform variants of the PsbA (D1) reaction center protein of Photosystem II. Under standard culture conditions Gloeobacter exhibits photosystem II electron transport, but several clear modifications in the redox potential of key cofactors bound by the PsbA protein are manifested in the flash-fluorescence characteristics. In other cyanobacteria dynamic expression of multiple psbA genes and turnover of PsbA isoforms is critical to counter excitation stress. We found that each of Gloeobacter's five psbA genes is expressed, with transcript abundances spanning 4.5 orders of magnitude. psbAI (glr2322) and psbAII (glr0779), encoding identical PsbA:2 form proteins, are constitutively expressed and dominate the psbA transcript pool under control conditions. psbAIII (gll3144) was strongly induced under photoinhibitory high irradiance stress, thereby contributing to a large increase in the psbA transcript pool that allowed cells to maintain their PsbA protein pools and then recover from irradiance stress, within one cellular generation. In contrast, under comparable photoinhibition provoked by UVB the cells were unable to maintain their psbA transcript and PsbA protein pools, and showed limited subsequent recovery. psbAIV (glr1706) and psbAV (glr2656), encoding two divergent PsbA isoforms, showed consistent trace expression but were never quantitatively significant contributors to the psbA transcript pool.
منابع مشابه
Identification of an oxygenic reaction center psbADC operon in the cyanobacterium Gloeobacter violaceus PCC 7421.
Gloeobacter violaceus, the earliest diverging oxyphotobacterium (cyanobacterium) on the 16S ribosomal RNA tree, has five copies of the photosystem II psbA gene encoding the D1 reaction center protein subunit. These copies are widely distributed throughout the 4.6 Mbp genome with only one copy colocalizing with other PSII subunits, in marked contrast to all other psbA genes in all publicly avail...
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متن کامل
Complete genome structure of Gloeobacter violaceus PCC 7421, a cyanobacterium that lacks thylakoids.
The nucleotide sequence of the entire genome of a cyanobacterium Gloeobacter violaceus PCC 7421 was determined. The genome of G. violaceus was a single circular chromosome 4,659,019 bp long with an average GC content of 62%. No plasmid was detected. The chromosome comprises 4430 potential protein-encoding genes, one set of rRNA genes, 45 tRNA genes representing 44 tRNA species and genes for tmR...
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ورودعنوان ژورنال:
- Biochimica et biophysica acta
دوره 1777 2 شماره
صفحات -
تاریخ انتشار 2008