Genetic factors of grain cadmium concentration in Polish wheat (Triticum polonicum L.)

• Published in: Plant physiology (Bethesda) 2024-10, Vol.196 (2), p.979-995
• Main Authors: Cheng, Yiran, Liu, Rui, Yang, Tian, Yang, Shan, Chen, Jia, Huang, Yiwen, Long, Dan, Zeng, Jian, Wu, Dandan, Kang, Houyang, Fan, Xing, Sha, Lina, Zhang, Haiqin, Zhou, Yonghong, Wang, Yi
• Format: Article
• Language: English
• Subjects: Cadmium - metabolism; Chromosome Mapping; Edible Grain - genetics; Edible Grain - metabolism; Phenotype; Plant Proteins - genetics; Plant Proteins - metabolism; Quantitative Trait Loci - genetics; Seeds - genetics; Seeds - metabolism; Triticum - genetics; Triticum - metabolism
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1093/plphys/kiae353

Wheat (Triticum aestivum L.) is one of the most important crops worldwide and a major source of human cadmium (Cd) intake. Limiting grain Cd concentration (Gr_Cd_Conc) in wheat is necessary to ensure food safety. However, the genetic factors associated with Cd uptake, translocation and distribution and Gr_Cd_Conc in wheat are poorly understood. Here, we mapped quantitative trait loci (QTLs) for Gr_Cd_Conc and its related transport pathway using a recombinant inbred line (RIL) population derived from 2 Polish wheat varieties (RIL_DT; dwarf Polish wheat [DPW] and tall Polish wheat [TPW]). We identified 29 novel major QTLs for grain and tissue Cd concentration; 14 novel major QTLs for Cd uptake, translocation, and distribution; and 27 major QTLs for agronomic traits. We also analyzed the pleiotropy of these QTLs. Six novel QTLs (QGr_Cd_Conc-1A, QGr_Cd_Conc-3A, QGr_Cd_Conc-4B, QGr_Cd_Conc-5B, QGr_Cd_Conc-6A, and QGr_Cd_Conc-7A) for Gr_Cd_Conc explained 8.16% to 17.02% of the phenotypic variation. QGr_Cd_Conc-3A, QGr_Cd_Conc-6A, and QGr_Cd_Conc-7A pleiotropically regulated Cd transport; 3 other QTLs were organ-specific for Gr_Cd_Conc. We fine-mapped the locus of QGr_Cd_Conc-4B and identified the candidate gene as Cation/Ca exchanger 2 (TpCCX2-4B), which was differentially expressed in DPW and TPW. It encodes an endoplasmic reticulum membrane/plasma membrane-localized Cd efflux transporter in yeast. Overexpression of TpCCX2-4B reduced Gr_Cd_Conc in rice. The average Gr_Cd_Conc was significantly lower in TpCCX2-4BDPW genotypes than in TpCCX2-4BTPW genotypes of the RIL_DT population and 2 other natural populations, based on a Kompetitive allele-specific PCR marker derived from the different promoter sequences between TpCCX2-4BDPW and TpCCX2-4BTPW. Our study reveals the genetic mechanism of Cd accumulation in wheat and provides valuable resources for genetic improvement of low-Cd-accumulating wheat cultivars.