Color-related chlorophyll and carotenoid concentrations of Chinese kale can be altered through CRISPR/Cas9 targeted editing of the carotenoid isomerase gene BoaCRTISO

Bo Sun,Yan Wang,Yun-Ting Zhang,Yuan-Xiu Lin,Wen-Li Huang,Xiao-Rong Wang,Yue Jian,Fen Zhang,Qiao Yuan,Hao-Ru Tang,Min Jiang,Hao Zheng,Qing Chen,Ai-Hong Zheng,Qiao-Mei Wang

doi:10.1038/s41438-020-00379-w

Bo Sun, Yan Wang + Show 13 more

Open Access

https://doi.org/10.1038/s41438-020-00379-w

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Abstract

The carotenoid isomerase gene (BoaCRTISO) of Chinese kale was targeted and edited using the CRISPR/Cas9 system in the present study. The results showed a high mutation rate (81.25%), and 13 crtiso mutants were obtained. Only two types of mutations, insertions and replacements, were found. Both the total and individual carotenoid and chlorophyll concentrations of the biallelic and homozygous mutants were reduced, and the total levels declined by 11.89–36.33%. The color of the biallelic and homozygous mutants changed from green to yellow, likely reflecting a reduction in the color-masking effect of chlorophyll on carotenoids. The expression levels of most carotenoid and chlorophyll biosynthesis-related genes, including CRTISO, were notably lower in the mutants than in the WT plants. In addition, the functional differences between members of this gene family were discussed. In summary, these findings indicate that CRISPR/Cas9 is a promising technique for the quality improvement of Chinese kale and other Brassica vegetables.

Highlights

Chinese kale (Brassica oleracea var. alboglabra) is a member of the Brassicaceae family, and the main edible parts of this plant are the highly nutritious tender leaves and bolting stems[1]
Su et al found that the loss of function of the BrCRTISO gene caused an accumulation of lycopene precursors in and an orange phenotype of Chinese cabbage[14]
Thirteen out of the 16 transgenic plants harbored mutations, including one biallelic mutant that accounted for 6.25% of the total number of mutations among the transgenic plants, five homozygous mutants that accounted for 31.25%, six heterozygous mutants that accounted for 37.5%, and one chimeric mutant that accounted for 6.25%

Summary

Introduction

Chinese kale (Brassica oleracea var. alboglabra) is a member of the Brassicaceae family, and the main edible parts of this plant are the highly nutritious tender leaves and bolting stems[1]. Carotenoids are a class of natural pigments that play important roles in photoprotection and antioxidant processes[4]. Their presence affects the color of many vegetables, fruits, and flowers, including those of tomato[5], carrot[6], cauliflower[7], watermelon[8], citrus[9], and lily[10]. Previous studies have shown that the loss of function of CRTISO results in a yellow color in several crop species, including tomato[12], rice[13], and Chinese cabbage[14]. Su et al found that the loss of function of the BrCRTISO gene caused an accumulation of lycopene precursors in and an orange phenotype of Chinese cabbage[14]

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