Cloning of plastid Acetyl-CoA carboxylase cDNA from Setaria italica and sequence analysis of graminicide target site

Acetyl-CoA carboxylase (ACCase) is a biotinylated enzyme that catalyzes the first committed step in fatty acid biosynthesis. Graminaceous ACCase in plastid is the target site of two classes of graminicide herbicides. Two full-length cDNAs of plastid ACCase from sethoxydim-resistant and sensitive Setaria Italica Beauv., named foxACC-Rand foxACC-S, have been cloned. cDNA sequencing showed that they encode a protein of 2 321 amino acids long with a pI of 5.89 and a calculated molecular mass of 256 kD. The sequences of foxACC-Rand foxACC-S have been compared with their homologs from other plants and analyzed for conserved amino acid regions and their functional domains. It is found that the amino acid at position 1 780 is Leu in foxACC R other than lie in foxACC-S and other cereal plastid ACCase. It is suspected that the change of Ile to Leu residue is critical for interaction of plastid ACCase with cereal herbicides APPs and CHDs. According to Southern hybridization, foxACC-R and foxACCLS are both estimated to be single copy in the genome of S. italica.