Isolation and analysis of structure and expression of low-temperature-induced genes in the cyanobacterium

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1. Low-temperature-induced genes, lti2, lti46, lti39 etc, were obtained by differential screening of the genomic DNA library of Anabaena variabilis M3.2. The nucleotide sequences of lti2 and lti46 were determined and the transcribed regions were located by nuclease S1 mapping. The gene lti2 was transcribed as a 2.0 knt RNA that encoded a polypeptide consisting of 552 amino acid residues which was homologous to alpha-amylases. The gene lti46 was a complex operon containing 3 open reading frames having sizes of 119,179 and 215 amino acid residues, respectively. The first orf was found in a 0.7 knt transcript, while the remaining orfs were found in a 1.6 knt transcript. A 2.5 knt transcript which contained all three orfs were also found. The second orf of lti46 was homologous to a surface antigen.3. The level of the transcripts of lti2 and lti46 genes increased rapidly within 1 hr after a low-temperature shift. The expression was transient and the steady-state level of the transcripts were quite low at both 38 and 22ﾟC.4. The promoter of lti2 was fused to the coding region of bacterial luciferase, and then transformed into Anabaena cells. The activity of luciferase increased 10-fold after a low-temperature shift. The activity was quite high in the cells adapted to a low temperature. The discrepancy between the expression of endogenous 1ti2 gene and that of the chimeric gene at 22ﾟC remains to be solved.