The promoter of a cytosolic glutamine synthetase gene from the conifer Pinus sylvestris is active in cotyledons of germinating seeds and light-regulated in transgenic Arabidopsis thaliana

We have isolated and characterized a genomic clone encoding Scots pine (Pin us sylvestris) cytosolic glutamine synthetase (GS), The clone contains the 5' end half of the gene including part of the coding region and 980 bp upst ream of the translation initiation codon. The major transcription start sit e (+1) was mapped around 180 nucleotides upstream of the translation initia tion codon. Sequence analysis of the 5'-upstream region of the gene reveals the presence of putative regulatory elements including a poly-CT consensus sequence, a purine-rich tandem repeat and two AT-rich regions. Fusions of the upstream gene region to uidA were shown to be transiently expressed in the cotyledons of germinating pine seeds transformed by microprojectile bom bardment. Stable transformation of Arabidopsis thaliana revealed the shoot apical meristem as the major region of heterologous permanent expression in Arabidopsis, in agreement with the expression of the GS gene in Pinus. Mor eover, quantitative data derived from fluorometric beta -glucuronidase assa ys in control and continuous Light-grown transgenic Arabidopsis plants indi cate that the isolated upstream region of the gene contains regulatory sequ ences involved in the response to light.