The glyoxylate cycle operates in oilseeds during postgerminative development when it is involved in the conversion of fatty acids released from lipid reserves, to sucrose, to support growth until the seedling becomes photosynthetically competent. Isocitrate lyase (ICL) and malate synthase (MS) are key enzymes of this cycle, serving to by-pass the carbon dioxide liberating steps of the Krebs' cycle. In cucumber, synthesis of these two enzymes is co-ordinately regulated during seedling development. Using the glyoxylate cycle as a model system, it is anticipated that an insight can be gained into the factors responsible for metabolic and developmental regulation of plant gene expression. A partial cDNA clone encoding ICL was sequenced and used as a probe in Southern analysis to reveal that the icl gene is single copy in cucumber. Transcript levels of both ICL and MS in seedlings up to eight days post-imbibition were analysed by Northern hybridisation and confirm co-ordinate expression of the two genes. A cucumber genomic library was constructed and a clone containing the icl gene was isolated. The nucleotide sequence was determined and the structure of the gene analysed. The start of transcription was mapped by primer extension. The 6.5 kb fragment carrying the icl gene was used to generate transgenic Nicotiana plumbaginifolia. Analysis of these transformants revealed that the transgene was faithfully transcribed following seed germination. Sequence comparisons of the promoter regions of the icl and ms genes revealed areas of homology potentially important in the co-ordinate transcriptional regulation of these genes. Gene fusion studies using the β-glucuronidase (GUS) reporter gene were carried out in both stable transformation and transient expression systems.