Abstract
BackgroundRice is a major food resource for Asian countries including Korea. However, most Asian countries are facing food safety problems due to cropland contamination by heavy metals. Thus, this study was conducted to investigate genetic factors affecting the expression of cadmium (Cd) gene, and to confirm differences in Cd translocation among cultivars because the current molecular understanding of Cd uptake-transport mechanisms remains insufficient. Associations between genotypes and gene expression level of Cd-related genes such as NRAMP, MTP, and HMA gene families in the rice core collection were analyzed at the genomic level.ResultsOs01g0956700, Os05g0128400 and Os11g0485200 showed strong associations between expression level and genotype in the rice core collection, the regulatory factors that associated with these genes in cis and trans were founded. The association between the expression level and genotype of the candidate gene (Os01g0611300: metal tolerance protein) predicted to affect Cd content in rice by a previous genome-wide association study (GWAS) was also analyzed. Furthermore, as a result of the phylogeny and haplotype analyses of the candidate gene, high-Cd tolerance cultivars were selected. The correlations between Cd and other inorganic components (Mg, Mn, Fe, Cu and Zn) in the roots, stems, leaves and unpolished grain of selected rice cultivars were analyzed.ConclusionTherefore, these results may be useful for understanding the uptake-transport mechanisms of Cd and other inorganic components via molecular genetics and may help rice breeders develop new low-Cd cultivars in the near future.
Highlights
Rice is a major food resource for Asian countries including Korea
GSH is synthesized by two adenosine triphosphate (ATP)-dependent reactions catalyzed by γ- glutamylcysteine synthetase and glutathione synthetase, which are present in the cytosol, and plant chloroplasts play a role in catalyzing these ATP-dependent reactions
Haplotypes and eQTLs of Os01g0956700 (OsLCD) Haplotype analyses of exon and intron sites revealed that the genotypes were divided into three groups
Summary
Rice is a major food resource for Asian countries including Korea. Most Asian countries are facing food safety problems due to cropland contamination by heavy metals. Cadmium (Cd) is a toxic material in the environment that threatens living organisms including humans and staple crops, through natural circulation in the food chain (Ogawa et al 2009). Plants synthesize Cys-rich and metalbinding peptides (phytochelatins (PCs) and metallothioneins) to eliminate toxicity when exposed to heavy metals (Clemens 2001). PCs are peptides synthesized from glutathiones (GSH) by PC synthase ((γ-Glu-Cys) 2–11-Gly); Cd detoxification occurs through a mechanism involving GSH and PCs (Mendoza-Cozatl et al 2005). The synthesized Cys provides a substrate for GSH biosynthesis (γ-ECS, GS) and phytochelatin biosynthesis (Mendoza-Cozatl et al 2005) (Additional file 1: Figure S1). APSK utilizes various metabolites such as phytosulfokines, steroids, glucosinates and sulfated flavonols, and synthesizes PAPS (Leustek and Saito 1999)
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