1 3 J Biol Inorg Chem DOI 10.1007/s00775-015-1281-3 ORIGINAL PAPER Elemental mapping of the entire intact Drosophila gastrointestinal tract Michael W. M. Jones 1,2 · Martin D. de Jonge 1 · Simon A. James 1 · Richard Burke 3 Received: 21 May 2015 / Accepted: 23 June 2015 © SBIC 2015 Malpighian tubules. This work simultaneously reveals dis- tribution of a number of biologically important elements in entire, intact GI tracts. These distributions revealed not only a previously undescribed Ca/Mn co-localization, but also the unexpected presence of additional Cu accumula- tions in the iron cell region. Keywords Drosophila · Metal ion absorption · Gastrointestinal tract · Synchrotron · X-ray fluorescence microscopy Introduction Essential biometals such as copper (Cu), iron (Fe) and zinc (Zn) play numerous roles in animal growth, development and maintenance, acting as structural or catalytic co-factors for collectively hundreds of proteins. The absolute require- ment for these dietary nutrients is reflected in the embry- onic lethality caused by mutation of mouse ion transporter genes such as Ctr1 (Cu uptake [1, 2]) and Zip4 (Zn uptake [3]) and the severe iron deficiency anaemia that results from deletion of divalent metal transporter 1 (DMT1, [4]). Biometals are selectively absorbed from the dietary con- tents of the gastrointestinal (GI) tract into the bloodstream by active transport across the apical (lumenal) and basolat- eral (circulatory) membranes of the intestinal enterocytes. For the most part, the metal transport proteins required for this absorption are well characterized. For example, Ctr1 is needed for uptake of Cu into the enterocytes [5] and ATP7A mediates Cu efflux across their basolateral mem- brane into the bloodstream [6], while for Zn, these func- tions are served by the Zip4 [7] and ZnT1 [8] proteins, respectively. Additionally, three pathways act to import dietary Fe into the enterocytes: uptake of heme by an as yet Abstract The main role of the animal gastrointestinal (GI) tract is the selective absorption of dietary nutrients from ingested food sources. One class of vital micronutri- ents are the essential biometals such as copper, zinc and iron, which participate in a plethora of biological process, acting as enzymatic or structural co-factors for numerous proteins and also as important cellular signalling mole- cules. To help elucidate the mechanisms by which biomet- als are absorbed from the diet, we mapped elemental dis- tribution in entire, intact Drosophila larval GI tracts using synchrotron X-ray fluorescence microscopy. Our results revealed distinct regions of the GI tract enriched for spe- cific metals. Copper was found to be concentrated in the copper cell region but also in the region directly anterior to the copper cells and unexpectedly, in the middle midgut/ iron cell region as well. Iron was observed exclusively in the iron cell region, confirming previous work with iron- specific histological stains. Zinc was observed throughout the GI tract with an increased accumulation in the pos- terior midgut region, while manganese was seen to co- localize with calcium specifically in clusters in the distal Electronic supplementary material The online version of this article (doi:10.1007/s00775-015-1281-3) contains supplementary material, which is available to authorized users. * Richard Burke richard.burke@monash.edu 1 Australian Synchrotron, 800 Blackburn Road, Clayton 3168, Australia 2 ARC Centre of Excellence for Advanced Molecular Imaging, Australian Synchrotron, 800 Blackburn Road, Clayton 3168, Australia 3 School of Biological Sciences, Monash University, Wellington Road, Clayton 3163, Australia