State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China.
Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, China.
J Exp Bot. 2019 Oct 24;70(20):5865-5878. doi: 10.1093/jxb/erz310.
Brassica rapa includes several important leafy vegetable crops with the potential for high cadmium (Cd) accumulation, posing a risk to human health. This study aims to understand the genetic basis underlying the variation in Cd accumulation among B. rapa vegetables. Cd uptake and translocation in 64 B. rapa accessions were compared. The role of the heavy metal ATPase gene BrHMA3 in the variation of Cd accumulation was investigated. BrHMA3 encodes a tonoplast-localized Cd transporter. Five full-length and four truncated haplotypes of the BrHMA3 coding sequence were identified, explaining >80% of the variation in the Cd root to shoot translocation among the 64 accessions and in F2 progeny. Truncated BrHMA3 haplotypes had a 2.3 and 9.3 times higher shoot Cd concentration and Cd translocation ratio, respectively, than full-length haplotypes. When expressed in yeast and Arabidopsis thaliana, full-length BrHMA3 showed activity consistent with a Cd transport function, whereas truncated BrHMA3 did not. Variation in the BrHMA3 promoter sequence had little effect on Cd translocation. Variation in the BrHMA3 coding sequence is a key determinant of Cd translocation to and accumulation in the leaves of B. rapa. Strong alleles of BrHMA3 can be used to breed for B. rapa vegetables that are low in Cd in their edible portions.
芸薹属包括几种具有高镉（Cd）积累潜力的重要叶菜类作物，对人类健康构成威胁。本研究旨在了解芸薹属蔬菜中 Cd 积累变异的遗传基础。比较了 64 个芸薹属品系的 Cd 吸收和转运。研究了重金属 ATP 酶基因 BrHMA3 在 Cd 积累变异中的作用。BrHMA3 编码一个液泡定位的 Cd 转运蛋白。鉴定了 BrHMA3 编码序列的 5 个全长和 4 个截断的单倍型，解释了 64 个品系和 F2 后代中 Cd 根到茎转运的变异的 80%以上。与全长单倍型相比，截断的 BrHMA3 单倍型的茎 Cd 浓度和 Cd 转运率分别高 2.3 倍和 9.3 倍。全长 BrHMA3 在酵母和拟南芥中表达时表现出与 Cd 运输功能一致的活性，而截断的 BrHMA3 则没有。BrHMA3 启动子序列的变异对 Cd 转运的影响很小。BrHMA3 编码序列的变异是 Cd 转运到和积累到芸薹属叶片中的关键决定因素。BrHMA3 的强等位基因可用于培育 Cd 含量低的可食用部分的芸薹属蔬菜。
