Description:

CrCD is a conditional negative selectable marker for use in the C. reinhardtii Chloroplast that confers sensitivity to 5-fluorocytosine by converting it to toxic 5-fluorouracil. Plasmid pRY127d contains the crCD gene, with a C-terminal HA tag, inserted into the Chloroplast expression vector pSRSapI. CrCD is a modified and codon-optimised version of the E. coli cytosine deaminase (codA) gene. The crCD gene in pRY127d uses the C. reinhardtii psaA exon 1 promoter and 5' UTR and the C. reinhardtii rbcL 3' UTR; the flanking regions in the construct target the crCD cassette downstream of psbH by homologous recombination.