Negative control of the high light-inducible hliA gene and implications for the activities of the NblS sensor kinase in the cyanobacterium Synechococcus elongatus strain PCC 7942
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The hliA gene of the cyanobacterium Synechococcus elongatus PCC 7942 is known to be upregulated by high-intensity light through the activity of the NblS sensor kinase. In this work it was found that, within the hliA upstream region, changes to the sequence around −30 to −25 (relative to the transcriptional start site) resulted in elevated hliA expression, implicating this region in negative regulation of the gene. Electrophoretic mobility shift assays performed were consistent with a protein binding this region that acts to keep the gene off in lower light. A reduction in gene dosage of nblS in vivo resulted in enhanced hliA expression, suggesting that negative control of hliA is mediated through NblS. An extended version of the high light regulatory 1 (HLR1) motif (previously described in Synechocystis PCC 6803) was identified within the sequence surrounding −30 to −25 of hliA. The extended HLR1 sequence was found upstream of other NblS-controlled genes from S. elongatus and Synechocystis PCC 6803 and upstream of hli genes from a variety of cyanobacterial and related genomes. These results point to the evolutionary conservation of the HLR1 element and its importance in NblS-mediated signaling and yield new insight into NblS-mediated control of gene expression.
KeywordsCyanobacteria High intensity light hliA gene HLR1 cis element NblS sensor kinase
High light regulatory 1 sequence
We thank Kavitha Salem for her help with RNA hybridizations and Kimberly Shahi for her help with GUS assays. This work was supported with funds to L.G.V. from The University of Texas at Arlington.
- Ausubel FM et al (2002) Current protocols in molecular biology. Wiley, HobokenGoogle Scholar
- Chow WS (1994) Photoprotection and photoinhibitory damage. In: Barber J (ed) Advances in molecular and cell biology. JAI Press, Greenwich, pp 151–196Google Scholar
- Onizuka T, Akiyama H, Endo S, Kanai S, Hirano M, Tanaka S, Miyasaka H (2002) CO2 response element and corresponding trans-acting factor of the promoter for ribulose-1,5-bisphosphate carboxylase/oxygenase genes in Synechococcus sp. PCC7002 found by an improved electrophoretic mobility shift assay. Plant Cell Physiol 43:660–667PubMedCrossRefGoogle Scholar
- Sambrook J, Fritsch EF, Maniatis T (1989) Molecular cloning: a laboratory manual, 2ndedn. Cold Spring Harbor Laboratory Press, Cold Spring HarborGoogle Scholar