Differential regulation of two glutamine synthetase genes by a single Dof transcription factor.
The PpDof5 transcription factor from maritime pine (Pinus pinaster) is a regulator of the expression of glutamine synthetase (GS) genes in photosynthetic and non-photosynthetic tissues. PpDof5 mRNA is detected almost ubiquitously during pine development with low levels of gene expression in green tissues and much higher levels in roots and lignified shoots. The PpDof5 protein expressed in bacteria binds to oligonucleotide probes containing the AAAG core sequence derived from the promoters of GS1a and GS1b genes. Transient expression experiments in agroinfiltrated tobacco leaves and in pine protoplasts demonstrated that PpDof5 is able to trans-regulate differentially the transcription of both GS1a and GS1b. PpDof5 activated transcription of the GS1b promoter and, in contrast, behaved as a transcriptional repressor of the GS1a promoter. These results support a regulatory mechanism for the transcriptional control of the spatial distribution of cytosolic GS isoforms in pine. Considering the precise expression patterns of GS1 genes required to fulfil the ammonium assimilation requirements during tree development, we hypothesize that PpDof5 could have a key role in the control of ammonium assimilation for glutamine biosynthesis in conifers. A regulatory model of GS1 gene expression in pine is proposed.
Departamento de Biología Molecular y Bioquímica, Instituto Andaluz de Biotecnología, Unidad Asociada UMA-CSIC, Campus Universitario de Teatinos, Universidad de Málaga, 29071 Málaga, Spain.
Marina
M
Rueda-López
Remedios
R
Crespillo
Francisco M
FM
Cánovas
Concepción
C
Avila
D002478:Cells, Cultured; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D017930:Genes, Reporter; D005974:Glutamate-Ammonia Ligase / Q000235:genetics* / Q000378:metabolism; D019697:Onions / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D028223:Pinus / Q000201:enzymology / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011523:Protoplasts / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D018076:DNA, Complementary; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds; D018749:RNA, Plant; D014157:Transcription Factors; D005974:Glutamate-Ammonia Ligase