Polymorphisms in the transit peptide of phytoene synthase ZmPSY1 link to the white color of grain endosperm in maize inbred lines

The yellow and orange color of Zea mays L. grain is determined by the presence of carotenoids, the first enzyme of the biosynthesis pathway of which is phytoene synthase PSY. In this study, we analyzed allelic variants of the ZmPSY1 gene in accessions of yellow-grain and white-grain maize inbred lines of domestic selection. In four lines with different grain colors, full-length ZmPSY1 cDNAs were amplified and sequenced, and their variability was characterized. In the cDNA sequence of ZmPSY1 from white-grain lines, nonsynonymous SNPs were found that lead to substitutions of four amino acid residues (L47I, W52S, E53D and A54V) in the N-terminal transit peptide responsible for the plastid localization of the enzyme. A primer system has been developed for PCR identification of the ZmPSY1 allele type in maize accessions. Testing of primers on 44 maize lines showed the presence of the wild-type ZmPSY1 allele and the absence of the mutant allele in the genome of all 22 yellow-grain lines analyzed. The mutant ZmPSY1 allele was detected in the genome of 41% of the 22 tested white-grain lines. The use of the developed primer system may be promising in the selection of corn with altered carotenoid content in the grain endosperm.