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- andβ-carotenes, while polymorphisms in ZmcrtRB3 contributed more variation in α-carotene than that inβ-carotene. Two single nucleotide polymorphisms （SNPs）, SNP1343 in 5＇untranslated region and SNP2172 in the second intron, consistently had effects on or-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 hapiotype 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.
Yi ZhouYingjia HanZhigang LiYang FuZhiyuan FuShutu XuJiansheng LiJianbing YanXiaohong Yang
