Abstract

During C4 photosynthesis, CO2 is concentrated around the enzyme RuBisCO in order to reduce photorespiration. The reactions in this pathway are typically distributed between mesophyll (M) and bundle sheath cells (BS). Genes can be recruited into M and BS cells in C4 leaves without alterations to cis-elements. For example, in the C4 plant, Cleome gynandra, the expression of a small family of decarboxylases (NAD-ME 1 & 2) is regulated by a 240 nucleotide sequence within the coding region of their transcripts. Results obtained to date identify two modules within the 240 nt sequence that are necessary for BS-cell specific expression of CgNAD-ME1. These modules are present in C3 Arabidopsis NAD -MEs and in the coding region of another family of decarboxylases, the NADP -ME family from Zea mays (C4) and Oryza sativa (C3). Initial analysis indicates that within the promoter region of CgNAD-ME1, at least one enhancer element could be increasing the levels of expression of CgNAD-ME1 compared with those generated by the AtNAD-ME1 promoter.