TRANSCRIPTIONAL AND POSTTRANSCRIPTIONAL CONTROL OF SUCROSE GENES IN SYNECHOCOCCUS SALT-TREATED CELLS

CUMINO A. C., M. PEREZ CENCI, G. CALÓ, G. L. SALERNO

Mar del Plata, Argentina (17-20 November)

Congreso; XLIII Meeting Annual SAIB; 2007

Argentine Society for Biochemestry and Moleculr Biology Research

Compatible solutes accumulate during cellular acclimation to environments with low water potentials. Synechococcus sp. PCC 7002 synthesizes glucosylglycerol (primary osmolite) and sucrose (Suc) in response to salt stress. Recently, it was elucidated that Suc synthesis in this strain occurs through the sequential action of sucrose-phosphate synthase (SPS) and sucrose-phosphate phosphatase (SPP). This strain presents a single gene that encodes SPS, in agreement with the proposed pattern of Suc metabolism evolution. SPS gene (spsA) is superimposed 8 nucleotides with the SPP gene (sppA), suggesting a transcripcional unit with two overlapped cistrons. We investigated the effect of NaCl and stationary phase on Suc gene expression in Synechococcus Northern blots revealed independent transcripts for both genes. We found that rifampicin abolished spsA and sppA transcript synthesis after 3 h of its addition. RT-PCR assays using intergenic primers were carried out to determine the possible presence of a bicistronic transcript. Only in the presence of chloramphenicol was detected the spsA/sppA transcriptional unit, suggesting that protein synthesis is involved in the primary transcript degradation, and that both genes are cotranscribed. Putative promoters were identified by primer extension analysis. This is the first report of a operon coordination of Suc synthesis gene expression.