title: Expression analysis of the Arabidopsis CP12 gene family suggests novel roles for these proteins in roots and floral tissues.
abstract: The chloroplast protein CP12 has been shown to regulate the activity of two Calvin cycle enzymes, phosphoribulokinase (PRK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), by the reversible formation of a multiprotein complex. In Arabidopsis there are three CP12 genes, CP12-1, CP12-2, and CP12-3, and expression analysis suggested that the function of these proteins may not be restricted to the Calvin cycle. Reverse transcription-PCR analysis was used here to investigate further the expression patterns of the three CP12 Arabidopsis genes together with the genes encoding plastid GAPDH (GAPA-1 and GAPB), PRK (PRK), and plastid NAD-dependent GAPDH (GAPCp1 and GAPCp2) during development, in response to changes in light, temperature, and anaerobic conditions. Expression of the CP12-2 gene was similar to that of the Calvin cycle enzymes PRK and GAPDH. However, this was not the case for CP12-1 and -3 which were both expressed in roots. Analysis of transgenic Arabidopsis lines expressing CP12::GUS fusion constructs revealed that the CP12 genes display different spatiotemporal expression patterns. The CP12-1 gene was expressed in root tips whilst CP12-3::GUS expression was evident throughout the root tissue. The most unexpected finding was that all three CP12 genes were expressed in floral tissues; CP12-1 and CP12-2 expression was detected in the sepals and the style of the flower, while in contrast CP12-3::GUS expression was restricted to the stigma and anthers. Taken together, the data suggest that the redox-sensitive CP12 proteins may have a wider role in non-photosynthetic plastids, throughout the plant life cycle.
authors.affiliation: Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK.
authors.forename: Prashant
authors.initials: P
authors.lastname: Singh
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Kaloudas
authors.forename: Christine A
authors.initials: CA
authors.lastname: Raines
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D035264:Flowers / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000528:radiation effects; D017930:Genes, Reporter; D047908:Intracellular Signaling Peptides and Proteins; D008027:Light; D005810:Multigene Family; D009928:Organ Specificity; D010802:Phylogeny; D018517:Plant Roots / Q000235:genetics* / Q000378:metabolism; D010944:Plants / Q000145:classification / Q000235:genetics; D021381:Protein Transport
chemical_list: D029681:Arabidopsis Proteins; C533605:CP12-1 protein, Arabidopsis; C533606:CP12-2 protein, Arabidopsis; C533607:CP12-3 protein, Arabidopsis; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins