Abstract
BackgroundCadmium (Cd) is a toxic heavy metal that is harmful to the environment and human health. Cd pollution threatens the cultivation of rice (Oryza sativa L.) in many countries. Improving rice performance under Cd stress could potentially improve rice productivity.ResultsIn this study, 9 growth traits of 188 different cultivated rice accessions under normal and Cd stress conditions were found to be highly variable during the seedling stage. Based on ~3.3 million single nucleotide polymorphisms (SNPs), 119 Cd-mediated growth response (CGR) quantitative trait loci (QTL) were identified by a genome-wide association study (GWAS), 55 of which have been validated by previously reported QTL and 64 were new CGR loci. Combined with the data from the GWAS, transcriptome analysis, gene annotations from the gene ontology (GO) Slim database, and annotations and functions of homologous genes, 148 CGR candidate genes were obtained. Additionally, several reported genes have been found to play certain roles in CGRs. Seven Cd-related cloned genes were found among the CGR genes. Natural elite haplotypes/alleles in these genes that increased Cd tolerance were identified by a haplotype analysis of a diverse mini core collection. More importantly, this study was the first to uncover the natural variations of 5 GST genes that play important roles in CGRs.ConclusionThe exploration of Cd-resistant rice germplasm resources and the identification of elite natural variations related to Cd-resistance will help improve the tolerance of current major rice varieties to Cd, as well as provide raw materials and new genes for breeding Cd-resistant varieties.
Highlights
Cadmium (Cd) is a toxic heavy metal that is harmful to the environment and human health
8 traits (i.e., sum of root length (SRL), root area (RA), superficial area of roots (SA), root volume (RV), maximum root length (MRL), shoot length (SL), shoot weight (SW), and root weight (RW)) decreased in varying degrees after Cd treatment (Table 1), while 5 traits (i.e., SRL, RA, SA, RV, and RW) were more sensitive, especially RV. These results were consistent with the findings of previous studies that found that Cd stress may inhibit the growth of seedlings [37, 38]
root diameter (RD) did not change under Cd stress, indicating that the growth of root thickness was not affected by Cd
Summary
Cadmium (Cd) is a toxic heavy metal that is harmful to the environment and human health. Cadmium (Cd) is a well-known heavy metal element that has a long decomposition cycle, easy migration, high toxicity, and is difficult to degrade, thereby posing a major threat to environmental safety and harming human health through the food chain in the form of biological enrichment [1]. When Cd accumulates to a certain extent, plants exhibit toxic symptoms, stunted root growth, and inhibited absorption of water and nutrients, leading to a series of physiological metabolic disorders, including blocked chlorophyll, sugar and protein synthesis, decreased photosynthesis, and altered enzymatic activities, which lead to reduced yield [4]. Cd mainly binds to proteins in plants and affects their growth and development by interfering with enzymatic activities, resulting in growth disorders [6]. The genetic basis of Cd effects on rice growth remains poorly studied
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