scholarly journals 5-Aminolevulinic Acid Availability and Control of Spectral Complex Formation in HemA and HemT Mutants of Rhodobacter sphaeroides :

1993 ◽  
Vol 175 (21) ◽  
pp. 7123-7123
Keyword(s):  
Complex Formation ◽  
Rhodobacter Sphaeroides ◽  
Aminolevulinic Acid ◽  
And Control ◽  
Spectral Complex

scholarly journals Interacting Regulatory Circuits Involved in Orderly Control of Photosynthesis Gene Expression in Rhodobacter sphaeroides 2.4.1

2000 ◽  
Vol 182 (11) ◽  
pp. 3081-3087 ◽  
Author(s):  
Jeong-Il Oh ◽  
Jesus M. Eraso ◽  
Samuel Kaplan
Keyword(s):  
Gene Expression ◽  
Complex Formation ◽  
Mutant Strain ◽  
Rhodobacter Sphaeroides ◽  
Photosynthetic Apparatus ◽  
Aerobic Conditions ◽  
Multiple Loci ◽  
Regulatory Circuits ◽  
Spectral Complex

ABSTRACT FnrL, the homolog of the global anaerobic regulator Fnr, is required for the induction of the photosynthetic apparatus inRhodobacter sphaeroides 2.4.1. Thus, the precise role of FnrL in photosynthesis (PS) gene expression and its interaction(s) with other regulators of PS gene expression are of considerable importance to our understanding of the regulatory circuitry governing spectral complex formation. Using a CcoP and FnrL double mutant strain, we obtained results which suggested that FnrL is not involved in the transduction of the inhibitory signal, by which PS gene expression is “silenced,” emanating from thecbb 3 oxidase encoded by the ccoNOQPoperon under aerobic conditions. The dominant effect of theccoP mutation in the FnrL mutant strain with respect to spectral complex formation under aerobic conditions and restoration of a PS-positive phenotype suggested that inactivation of thecbb 3 oxidase to some extent bypasses the requirement for FnrL in the formation of spectral complexes. Additional analyses revealed that anaerobic induction of thebchE, hemN, and hemZ genes, which are involved in the tetrapyrrole biosynthetic pathways, requires FnrL. Thus, FnrL appears to be involved at multiple loci involved in the regulation of PS gene expression. Additionally, bchE was also shown to be regulated by the PrrBA two-component system, in conjunction with hemN and hemZ. These and other results to be discussed permit us to more accurately describe the role of FnrL as well as the interactions between the FnrL, PrrBA, and other regulatory circuits in the regulation of PS gene expression.

Chilling-induced chlorosis in maize (Zea mays)

1985 ◽  
Vol 63 (4) ◽  
pp. 711-715 ◽  
Author(s):  
R. Hodgins ◽  
R. B. van Huystee
Keyword(s):  
Zea Mays ◽  
Chlorophyll Content ◽  
Sweet Corn ◽  
Aminolevulinic Acid ◽  
Chlorophyll Synthesis ◽  
Carotenoid Content ◽  
Control Tissue ◽  
Etiolated Seedlings ◽  
Chilling Temperatures ◽  
And Control

The effect of chilling temperatures on the porphyrin pathway leading to chlorophyll was studied in Seneca Chief hybrid sweet corn. One-week-old seedlings grown at 28 °C in a 14 h light: 10 h dark photoperiod synthesize negligible amounts of chlorophyll when exposed to 12 °C for a subsequent 6 d. When the chilled plant is then brought back to 28 °C, chlorophyll synthesis is restored to control levels. Little difference in carotenoid content was detected between chill-stressed and control tissue even after 4 d of stress. Small differences in the chlorophyll content per 106 chloroplasts could be detected between stressed and control seedlings. Etiolated seedlings synthesize negligible amounts of chlorophyll or its precursors when illuminated at 12 °C. Incubation of tissue with aminolevulinic acid at various temperatures from 12 to 22 °C resulted in an accumulation of precursors comparable to 28 °C control tissue. The ability of etiolated tissue to accumulate aminolevulinic acid was negligible when illuminated at 12 °C as compared with that in tissue illuminated at 28 °C.

scholarly journals Regulation of the Rhodobacter sphaeroides 2.4.1 hemA Gene by PrrA and FnrL

2008 ◽  
Vol 190 (20) ◽  
pp. 6769-6778 ◽  
Author(s):  
Britton Ranson-Olson ◽  
Jill H. Zeilstra-Ryalls
Keyword(s):  
Binding Site ◽  
Rhodobacter Sphaeroides ◽  
Binding Sites ◽  
Aminolevulinic Acid ◽  
Acid Synthesis ◽  
P2 Promoter ◽  
Indirect Action ◽  
Hema Gene

ABSTRACT Part of the oxygen responsiveness of Rhodobacter sphaeroides 2.4.1 tetrapyrrole production involves changes in transcription of the hemA gene, which codes for one of two isoenzymes catalyzing 5-aminolevulinic acid synthesis. Regulation of hemA transcription from its two promoters is mediated by the DNA binding proteins FnrL and PrrA. The two PrrA binding sites, binding sites I and II, which are located upstream of the more-5′ hemA promoter (P1), are equally important to transcription under aerobic conditions, while binding site II is more important under anaerobic conditions. By using phosphoprotein affinity chromatography and immunoblot analyses, we showed that the phosphorylated PrrA levels in the cell increase with decreasing oxygen tensions. Then, using both in vivo and in vitro methods, we demonstrated that the relative affinities of phosphorylated and unphosphorylated PrrA for the two binding sites differ and that phosphorylated PrrA has greater affinity for site II. We also showed that PrrA regulation is directed toward the P1 promoter. We propose that the PrrA component of anaerobic induction of P1 transcription is attributable to higher affinity of phosphorylated PrrA than of unphosphorylated PrrA for binding site II. Anaerobic activation of the more-3′ hemA promoter (P2) is thought to involve FnrL binding to an FNR consensuslike sequence located upstream of the P2 promoter, but the contribution of FnrL to P1 induction may be indirect since the P1 transcription start is within the putative FnrL binding site. We present evidence suggesting that the indirect action of FnrL works through PrrA and discuss possible mechanisms.

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