Characterization of BoaCRTISO Reveals Its Role in Carotenoid Biosynthesis in Chinese Kale.

Min Jiang,Peixing Lin,Qiao Yuan,Qiaomei Wang,Sha Liang,Fen Zhang,Bo Sun,Yue Jian,Huiying Miao,Hao Zheng,Huanxiu Li

doi:10.3389/fpls.2021.662684

Min Jiang, Peixing Lin + Show 9 more

Open Access

https://doi.org/10.3389/fpls.2021.662684

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Abstract

Carotenoids are organic pigments that play an important role in both plant coloration and human health; they are a critical subject in molecular breeding due to growing demand for natural molecules in both food and medicine. In this study, we focus upon characterizing BoaCRTISO, the carotenoid isomerase gene before the branch of the carotenoid biosynthetic pathway, which is expressed in all organs and developmental stages of Chinese kale, and BoaCRTISO, which is located in the chloroplast. The expression of BoaCRTISO is induced by strong light, red and blue combined light, and gibberellic acid treatment, but it is suppressed by darkness and abscisic acid treatment. We obtained BoaCRTISO-silenced plants via virus-induced gene silencing technology, and the silence efficiencies ranged from 52 to 77%. The expressions of most carotenoid and chlorophyll biosynthetic genes in BoaCRTISO-silenced plants were downregulated, and the contents of carotenoids and chlorophyll were reduced. Meanwhile, BoaCRTISO-silenced plants exhibited phenotypes of yellowing leaves and inhibited growth. This functional characterization of BoaCRTISO provides insight for the biosynthesis and regulation of carotenoid in Chinese kale.

Highlights

Chinese kale (Brassica oleracea var. alboglabra) is a member of Brassicaceae, or the mustard family, which originated in South China and later spread throughout Southeast Asia (Lei et al, 2017)
A phylogenetic analysis showed that BoaCRTISO clustered with other Cruciferae carotenoid isomerase (CRTISO) (Figure 1B), which indicates that CRTISO is highly conserved in cruciferous plants
A construct encoding BoaCRTISO fused to green fluorescent protein (GFP) was transformed into Chinese kale protoplasts, and strong fluorescence from GFP-BoaCRTISO was detected in the chloroplast (Figure 1C), which clearly demonstrates that BoaCRTISO localizes to the chloroplast

Summary

Introduction

Chinese kale (Brassica oleracea var. alboglabra) is a member of Brassicaceae, or the mustard family, which originated in South China and later spread throughout Southeast Asia (Lei et al, 2017). Our previous studies have shown that Chinese kale is rich in health-promoting compounds including vitamin C, glucosinolates, and carotenoids (Sun et al, 2012a,b). Carotenoids are the second largest group of natural pigments and are known to play crucial roles in plant color, photosynthesis, and human health (Xiao et al, 2012). The different types and contents of carotenoids lead to the rich and colorful red, yellow, and orange pigments of vegetables, fruits, and flowers such as tomato (Ye et al, 2015), citrus (Kato et al, 2004), watermelon (Lv et al, 2015), and chrysanthemum (Yamagishi et al, 2010). Carotenoids are necessary to maintain body health.

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