Reporter construct used for mutant screen and verification of ASN1 gene expression in cli186. (a) Schematic representation showing regulation of the ASN1-HPT2 reporter construct used to select for c arbon and l ight i nsensitive (cli) plants. A 148-bp region of the ASN1 promoter from pea was placed upstream of the hygromycin phosphotransferase gene, HPT2. ASN1 is transcriptionally repressed by sucrose and by light independently, where sucrose and light together have a synergistic repressive effect. (b) Three mutagenized lines, cli186, cli12-2-1 and cli16-1 that exhibit hygromycin-resistance when screened on 0.5% sucrose in L/D cycling conditions. Controls consist of a 'wild-type' (WT) unmutagenized line containing the ASN1-HPT2 transgene and a transgenic line (NOS) containing the HPT2 transgene driven by a NOS promoter, allowing for constitutive expression of the HPT2 gene. (c) Fold-repression as determined via Q-PCR of ASN1 in WT and cli186 plants. Seven day old etiolated seedlings were subject to four treatments: -C-L, +C-L, -C+L and +C+L. Fold-repression of ASN1 was determined by comparing all treatments against their respective backgrounds of -C-L. Asterisks indicate a significant difference between WT and cli186 in expression based on a t-test, p > 0.05.