Distinct cis-acting sequences are required for the germination and sugar responses of the cucumber isocitrate lyase gene.

Recent data have shown that distinct DNA sequence elements direct the germination and sugar responses of the cucumber (Cucumis sativus, L.) malate synthase (Ms) gene (Sarah et al. (1996) Mol. Gen. Genet., 250, 153-161). Such information is, however, lacking for the isocitrate lyase (Icl) gene which is coordinately regulated with Ms. Deletions from the 5' end of the Icl promoter were therefore created specifically to address this question. Analysis of expression in seeds of transgenic Nicotiana plumbaginifolia plants showed that whereas a promoter sequence of 2.9 kilobases (kb) produced a normal germination response, deletion to -1568 base pairs (bp) dramatically reduced this response. Examination of the sugar response employed a transgenic cucumber root system. In this case, the 2900 bp and 1568 bp promoters both gave a strong sugar response, but further deletion to -1367 bp eliminated the response. Therefore, the germination and sugar responses of the Icl gene require distinct cis-acting elements, located respectively upstream and downstream of -1568 bp. This observation is consistent with distinct signal transduction systems regulating gene expression in each case.