Tracking sulfur and phosphorus within single starch granules using synchrotron X-ray microfluorescence mapping

• Published in: Biochimica et biophysica acta Vol. 1840; no. 1; pp. 113 - 119
• Main Authors: Buléon, Alain, Cotte, Marine, Putaux, Jean-Luc, d'Hulst, Christophe, Susini, Jean
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2014; Elsevier
• Subjects: amylopectin; amylose; Arabidopsis; biosynthesis; carbohydrate structure; Chemical and Process Engineering; Chlamydomonas; corn starch; Cytoplasmic Granules - metabolism; Engineering Sciences; fluorescence; Food engineering; genetic background; glucose; Granule bound starch synthase; granules; Life Sciences; Micro X-ray fluorescence; mutants; phosphates; Phosphorus; Phosphorus - metabolism; phosphorylation; polymers; potato starch; potatoes; proteins; Solanum tuberosum - growth & development; Solanum tuberosum - metabolism; Spectrometry, X-Ray Emission - instrumentation; Spectrometry, X-Ray Emission - methods; Starch; Starch - metabolism; starch granules; starch synthase; Starch Synthase - metabolism; Sulfur; Sulfur - metabolism; Synchrotron; Synchrotrons; Triticum - growth & development; Triticum - metabolism; X-radiation; Phosphorus; Micro X-ray fluorescence; Synchrotron; Sulfur; Starch; Granule bound starch synthase
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2013.08.029

Native starch accumulates as granules containing two glucose polymers: amylose and amylopectin. Phosphate (0.2–0.5%) and proteins (0.1–0.7%) are also present in some starches. Phosphate groups play a major role in starch metabolism while granule-bound starch synthase 1 (GBSS1) which represents up to 95% of the proteins bound to the granule is responsible for amylose biosynthesis. Synchrotron micro-X-ray fluorescence (μXRF) was used for the first time for high-resolution mapping of GBSS1 and phosphate groups based on the XRF signal of sulfur (S) and phosphorus (P), respectively. Wild-type starches were studied as well as their related mutants lacking GBSS1 or starch-phosphorylating enzyme. Wild-type potato and maize starch exhibited high level of phosphorylation and high content of sulfur respectively when compared to mutant potato starch lacking glucan water dikinase (GWD) and mutant maize starch lacking GBSS1. Phosphate groups are mostly present at the periphery of wild-type potato starch granules, and spread all over the granule in the amylose-free mutant. P and S XRF were also measured within single small starch granules from Arabidopsis or Chlamydomonas not exceeding 3–5μm in diameter. Imaging GBSS1 (by S mapping) in potato starch sections showed that the antisense technique suppresses the expression of GBSS1 during biosynthesis. P mapping confirmed that amylose is mostly present in the center of the granule, which had been suggested before. μXRF is a potentially powerful technique to analyze the minor constituents of starch and understand starch structure/properties or biosynthesis by the use of selected genetic backgrounds. [Display omitted] •P (phosphate groups) and S (GBSS1) are present in very limited amount in starch.•First synchrotron X-ray microfluorescence mapping of P and S in single starch granules•Antisense technique suppresses expression of GBSS1 during biosynthesis.•Phosphate groups are mostly present at the periphery of potato starch granules.•P mapping suggests that amylose is more present in the center of the starch granule.