The Arabidopsis PPDK gene is transcribed from two promoters to produce differentially expressed transcripts responsible for cytosolic and plastidic proteins

The Arabidopsis PPDK gene is transcribed from two promoters to produce differentially expressed... Pyruvate orthophosphate dikinase (PPDK) is a critical enzyme for C4 photosynthesis, providing the primary acceptor for fixation of bicarbonate in mesophyll cells. Although first isolated in C4 plants, it is also present in C3 species. We report that the single gene encoding PPDK in Arabidopsis thaliana possesses two promoters, giving rise to two types of transcript. The longer transcript is generated from a promoter upstream of the first exon, while the shorter transcript is derived from a promoter found within the first intron of the longer form. Apart from 5′ untranslated regions, the presence of the first exon, and three missing codons at the start of the second exon in the longer form, the transcripts are identical. Fusions between the two forms of transcript and gfp showed that the longer transcript encodes a protein targeted to the chloroplast, that its first exon acts as a transit peptide, and that the smaller protein is cytosolic. Abundance of the shorter transcript, responsible for producing the cytosolic protein increases rapidly and specifically during extended dark and dark-induced senescence. Transcripts for both chloroplastic and cytosolic proteins were detectable in cotyledons, while in cauline leaves the transcript encoding the chloroplastic protein was most abundant. We propose that in cotyledons PPDK may be important in supplying PEP to gluconeogenesis, and in ageing leaves it allows remobilisation of nitrogen to supply reproductive tissue. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Molecular Biology Springer Journals

The Arabidopsis PPDK gene is transcribed from two promoters to produce differentially expressed transcripts responsible for cytosolic and plastidic proteins

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Publisher
Kluwer Academic Publishers
Copyright
Copyright © 2006 by Springer Science+Business Media B.V.
Subject
Life Sciences; Plant Pathology; Plant Sciences ; Plant Sciences
ISSN
0167-4412
eISSN
1573-5028
D.O.I.
10.1007/s11103-006-9023-0
Publisher site
See Article on Publisher Site

Abstract

Pyruvate orthophosphate dikinase (PPDK) is a critical enzyme for C4 photosynthesis, providing the primary acceptor for fixation of bicarbonate in mesophyll cells. Although first isolated in C4 plants, it is also present in C3 species. We report that the single gene encoding PPDK in Arabidopsis thaliana possesses two promoters, giving rise to two types of transcript. The longer transcript is generated from a promoter upstream of the first exon, while the shorter transcript is derived from a promoter found within the first intron of the longer form. Apart from 5′ untranslated regions, the presence of the first exon, and three missing codons at the start of the second exon in the longer form, the transcripts are identical. Fusions between the two forms of transcript and gfp showed that the longer transcript encodes a protein targeted to the chloroplast, that its first exon acts as a transit peptide, and that the smaller protein is cytosolic. Abundance of the shorter transcript, responsible for producing the cytosolic protein increases rapidly and specifically during extended dark and dark-induced senescence. Transcripts for both chloroplastic and cytosolic proteins were detectable in cotyledons, while in cauline leaves the transcript encoding the chloroplastic protein was most abundant. We propose that in cotyledons PPDK may be important in supplying PEP to gluconeogenesis, and in ageing leaves it allows remobilisation of nitrogen to supply reproductive tissue.

Journal

Plant Molecular BiologySpringer Journals

Published: Aug 17, 2006

References

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