Fast X-ray fluorescence microscopy provides high-throughput phenotyping of element distribution in seeds

The concentration, chemical speciation, and spatial distribution of essential and toxic mineral elements in cereal seeds have important implications for human health. To identify genes responsible for element uptake, translocation, and storage, high-throughput phenotyping methods are needed to visualize element distribution and concentration in seeds. Here, we used X-ray fluorescence microscopy (mu-XRF) as a method for rapid and high-throughput phenotyping of seed libraries and developed an ImageJ-based pipeline to analyze the spatial distribution of elements. Using this method, we nondestructively scanned 4,190 ethyl methanesulfonate (EMS)-mutagenized M1 rice (Oryza sativa) seeds and 533 diverse rice accessions in a genome-wide association study (GWAS) panel to simultaneously measure concentrations and spatial distribution of elements in the embryo, endosperm, and aleurone layer. A total of 692 putative mutants and 65 loci associated with the spatial distribution of elements in rice seed were identified. This powerful method provides a basis for investigating the genetics and molecular mechanisms controlling the accumulation and spatial variations of mineral elements in plant seeds. Fast X-ray fluorescence microscopy (mu-XRF) provides a high-throughput method to investigate the mechanisms controlling the accumulation and spatial variations of mineral elements in plant seeds.

Automated summary

The concentration, chemical speciation, and spatial distribution of essential and toxic mineral elements in cereal seeds have significant implications for human health. X-ray fluorescence microscopy (mu-XRF) is used to identify genes responsible for element uptake, translocation, and storage, and an ImageJ-based pipeline is developed for spatial distribution analysis. This method is applied in rice seeds and diverse rice accessions, identifying loci and mutants associated with the spatial distribution of elements and providing a basis for investigating the genetics and molecular mechanisms controlling mineral elements in plant seeds.