α-carotene is one of the important components of pro-vitamin A, which is able to be converted into vitamin A in the human body. One maize (Zea mays L.) ortholog of carotenoid hydroxylases in Arabidopsis thaliana, ZmcrtRB3, was cloned and its role in carotenoid hydrolyzations was addressed. ZmcrtRB3 was mapped in a quantitative trait locus (QTL) cluster for carotenoid-related traits on chromosome 2 (bin 2.03) in a recombinant inbred line (RIL) population derived from By804 and B73. Candidate-gene association analysis identified 18 polymorphic sites in ZmcrtRB3 significantly associated with one or more carotenoid-related traits in 126 diverse yellow maize inbred lines. These results indicate that the enzyme ZmcrtRB3 plays a role in hydrolyzing both α- and β-carotenes, while polymorphisms in ZmcrtRB3 contributed more variation in α-carotene than that in β-carotene. Two single nucleotide polymorphisms (SNPs), SNP1343 in 5′untranslated region and SNP2172 in the second intron, consistently had effects on α-carotene content and composition with explained phenotypic variations ranging from 8.7% to 34.8%. There was 1.7- to 3.7-fold change between the inferior and superior haplotype for α-carotene content and composition. Thus, SNP1343 and SNP2172 are potential polymorphic sites to develop functional markers for applying marker-assisted selection in the improvement of pro-vitamin A carotenoids in maize kernels.
Zhou, Y.; Han, Y.; Li, Z.; Fu, Y.; Fu, Z.; Xu, S.; Li, J.; Yan, J.; Yang, X. ZmcrtRB3 Encodes a Carotenoid Hydroxylase that Affects the Accumulation of &#945;-carotene in Maize KernelF. Journal of Integrative Plant Biology (2012) 54 (4) 260-269. [DOI: 10.1111/j.1744-7909.2012.01106.x]