Transcriptome and Re-Sequencing Analyses Reveal Photosynthesis-Related Genes Involvement in Lutein Accumulation in Yellow Taproot Mutants of Carrot

Abstract

Carrots accumulate numerous carotenoids in the root, resulting in different colors. Orange carrots are primarily high in α- and β-carotene, while yellow carrots are packed with lutein. This study was designed to explore the molecular mechanism underlying the yellow mutation involving lutein using a recently obtained yellow root mutant carrot (ym) via mutagenesis of an orange root wild type (wt). Microscopes were used to observe the variations in histological and cellular structures, and transcriptome and resequencing analyses were conducted for ym and wt. The root callus of ym contained fewer colored crystals and globular chromoplasts than those of wt. Based on ribonucleic acid sequencing (RNA-seq) data analysis, 19 photosynthesis-related differentially expressed genes (DEGs) were enriched. Among them, there were 6 photosynthesis-related genes experiencing nonsynonymous mutations, including PSAL, PSB27-1, psbB, and three homologs of LHCB1.3, and Lut 5, the mapped gene regulating lutein content in carrot root, also had nonsynonymous mutations in ym. These 7 genes were shown to be significantly differently expressed at one or more time points during the lutein accumulation process. It is predicted that the 6 photosynthesis-related genes and Lut 5 are candidate genes for lutein accumulation, which results in root color mutation. The candidate genes identified in this study can provide a new insight into the molecular mechanism of lutein modulation.