Carotenoid composition and expression of biosynthetic genes in yellow and white foxtail millet [Setaria italica (L.) Beauv]

Abstract Foxtail millet [ Setaria italica (L.) Beauv], an important minor crop in semi-arid regions of Northern China, is valued for its flavor, color and nutrition. In order to understand the relationship between carotenoid accumulation and expression of related genes in foxtail millet, two contrasting varieties were studied. 'Jingu21', which produces yellow millet and 'Zhisheng', white millet, were analyzed for the accumulation and composition of millet carotenoids and for the expression profiles of genes involved in their metabolism.The total yellow pigment content in Jingu21 was 19.23 mg kg −1 due to the high levels of lutein (13.58 mg kg −1 ) and zeaxathin (3.77 mg kg −1 ), whereas Zhisheng contained only 2.01 mg kg −1 with 0.81 mg kg −1 lutein and 0.22 mg kg −1 zeaxathin. The expression patterns of 14 carotenoid-related genes at different grain maturing stages indicated that the marked differences in the accumulation of carotenoids in foxtail millet might be explained by the continued up-regulation of SiPSY1 accompanied by the significant down-regulation of SiCCD1 in Jingu21.