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The effects of high concentrations of salts on photosynthetic electron transport in spinach (Spinacia oleracea) chloroplasts.

ABSTRACT: 1. Photosynthetic electron transport from water to lipophilic Photosystem II acceptors was stimulated 3--5-fold by high concentrations (greater than or equal to 1 M) of salts containing anions such as citrate, succinate and phosphate that are high in the Hofmeister series. 2. In trypsin-treated chloroplasts, K3Fe(CN)6 reduction insensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea was strongly stimulated by high concentrations of potassium citrate, but there was much less stimulation of 2,6-dichloroindophenol reduction in Tris-treated chloroplasts supplied with 1,5-diphenylcarbazide as artificial donor. The results suggest that the main site of action of citrate was the O2-evolving complex of Photosystem II. 3. Photosystem I partial reactions were also stimulated by intermediate concentrations of citrate (up to 2-fold stimulation by 0.6--0.8 M-citrate), but were inhibited at the highest concentrations. The observed stimulation may have been caused by stabilizaton of plastocyanin that was complexed with the Photosystem I reaction centre, 4. At 1 M, potassium citrate protected O2 evolution against denaturation by heat or by the chaotropic agent NaNO3. 5. It is suggested that anions high in the Hofmeister series stimulated and stabilized electron transport by enhancing water structure around the protein complexes in the thylakoid membrane.

SUBMITTER: Stewart AC

PROVIDER: S-EPMC1158410 | biostudies-other | 1982 Jun

REPOSITORIES: biostudies-other

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Stromal protein phosphorylation in spinach (Spinacia oleracea) chloroplasts.

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The complete mitochondrial genome sequence of spinach, <i>Spinacia oleracea</i> L.

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2020-06-24 | GSE153070 | GEO

Spinacia oleracea strain:Spinach

Project description:Spinacia oleracea strain:Spinach Raw sequence reads

| PRJNA576552 | ENA

Alternative mRNA splicing of 3'-terminal exons generates ascorbate peroxidase isoenzymes in spinach (Spinacia oleracea) chloroplasts.

Project description:We have isolated two cDNA clones encoding spinach (Spinacia oleracea) stromal and thylakoid-bound ascorbate peroxidase isoenzymes [Ishikawa, Sakai, Yoshimura, Takeda and Shigeoka (1996) FEBS Lett. 384, 289-293]. The gene (ApxII) encoding both chloroplastic ascorbate peroxidase isoenzymes was isolated and the organization of the gene was determined. Alignment between the cDNAs and the gene for chloroplastic ascorbate peroxidase isoenzymes indicates that both enzymes arise from a common pre-mRNA by alternative splicing of two 3'-terminal exons. Genomic Southern-blot analysis supported this finding. The gene spanned nearly 8.5 kbp and contained 13 exons split by 12 introns. The penultimate exon 12 (residues 7376-7530) for the stromal ascorbate peroxidase mRNA consisted of one codon for Asp365 before the TAA termination codon, and the entire 3'-untranslated region, including a potential polyadenylation signal (AATAAA). The final exon 13 (residues 7545-7756) for the thylakoid-bound ascorbate peroxidase mRNA consisted of the corresponding coding sequence of the hydrophobic C-terminal region, the TGA termination codon and the entire 3'-untranslated region, including a potential polyadenylation signal (AATATA). Both exons were interrupted by a 14 bp non-coding sequence. Northern-blot and reverse transcription-PCR analysis showed that the transcripts for stromal and thylakoid-bound ascorbate peroxidase are present in spinach leaves.

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