The phosphorus concentration in starch was determined by fluorescent X-ray analysis using the standard curve method (Otaka et al. 2014 (
link); Watanabe et al. 2021 ). The standard curves for phosphorus were constructed using the representative plant certified reference materials, apple leaves (NIAS SRM 1515), pepperbush (NIES CRM No.1), Chlorella (NIES CRM No.3), and tea leaves (NIES CRM No.23). Tuber starch was lyophilized, and the dried starch sample was ground using a mixer mill (MM400, Retsch, Haan, Germany). Three hundred milligrams of the starch powder was used to make a 20 mm diameter tablet using a manual hydraulic press (
GS15011; Specac Ltd., Orpington, UK) at 9 tons of pressure for 10 min. The obtained tablets were provided for the analysis of phosphorus molecules and other elements by an energy dispersive X-ray fluorescence (XRF) spectrometer (Epsilon 5; Malvern Panalytical, Spectris, The Netherlands). The phosphorus concentrations were compared between the wild type and mutants and are indicated by the values relative to that of the WT. The data were statistically analyzed using Dunnett’s multiple comparison test.
Ohnuma M., Ito K., Hamada K., Takeuchi A., Asano K., Noda T., Watanabe A., Hokura A., Teramura H., Takahashi F., Mutsuro-Aoki H., Tamura K, & Shimada H. (2023). Peculiar properties of tuber starch in a potato mutant lacking the α-glucan water dikinase 1 gene GWD1 created by targeted mutagenesis using the CRISPR/dMac3-Cas9 system. Plant Biotechnology, 40(3), 219-227.
