Isolation and characterization of induced mutants in the gene associated with seed cadmium accumulation in soybean

Abstract

Food contamination by cadmium (Cd) is a serious threat to human health. Thus, it is imperative to prevent Cd accumulation in staple crops like soybean. The development of low Cd accumulating cultivars is an effective solution. To this end, it is essential to identify the gene(s) controlling seed Cd accumulation. Although Glyma.09G055600 (GmHMA3) seems to be associated with Cd accumulation in soybean, it has not been established if it is responsible for seed Cd accumulation. In the present study, the effect of GmHMA3 on seed Cd accumulation in soybean was validated using three independent GmHMA3 mutants isolated from an ethyl methanesulfonate-induced soybean mutant library. Each of mutant had an amino acid substitution in GmHMA3 and segregating progenies were developed by crossing the original cultivar with each of the three mutants. The relationship between these three mutations and seed Cd accumulation was investigated. While two of them significantly increased seed Cd accumulation corresponding to previous reports of a natural missense mutation in GmHMA3, the other slightly decreased seed Cd accumulation. Overall, these results indicate that GmHMA3 is responsible for seed Cd accumulation in soybean.

Keywords: GmHMA3; amino acid substitution; cadmium (Cd); mutant; soybean.

Fig. 1

Schematic structure of the GmHMA3 regions amplified for mutant screening. Boxes, lines, and bold bidirectional arrows denote exons, introns, and amplified regions for mutant screening, respectively.

Fig. 2

Amino acid alignments in the first, seventh, eighth, and ninth exons of GmHMA3 in ‘Fukuyutaka’, M1, M3, M5, and ‘Harosoy’. Metal-binding domain, HP motif, and GDGxNDx motif are indicated in gray. Mutation points of M1, M3, M5, and ‘Harosoy’ in relation to ‘Fukuyutaka’ are indicated in boxes. Amino acid alignment of ‘Harosoy’ was obtained from Benitez et al. (2012).