Contrasting calcium localization and speciation in leaves of Medicago truncatula mutant COD5 analyzed via synchrotron X-ray techniques.

The Plant journal : for cell and molecular biology

PubMedID: 24033783

Punshon T, Tappero R, Ricachenevsky FK, Hirschi K, Nakata PA. Contrasting calcium localization and speciation in leaves of Medicago truncatula mutant COD5 analyzed via synchrotron X-ray techniques. Plant J. 2013;.
Oxalate-producing plants accumulate calcium oxalate crystals (CaOx(c) ) in the range of 3-80%(w/w) of their dry weight, reducing calcium (Ca) bioavailability. The calcium oxalate deficient 5 (cod5) mutant of Medicago truncatula has been previously shown to contain similar Ca, but lower oxalate and CaOx(c) concentrations than wild type (WT) plants. We imaged the Ca distribution in WT and cod5 leaflets via synchrotron X-ray fluorescence mapping (SXRF). We observed a contrast in the Ca distribution between cod5 and WT leaflets, manifested as an abundance of Ca in the interveinal areas and a lack of Ca along the secondary veins in cod5, the opposite of WT. X-ray microdiffraction (µXRD) of M. truncatula leaves confirmed crystalline CaOx(c) (whewellite; CaC2 O4 •H2 O) was present in WT only, in cells sheathing the secondary veins. Together with µXRD, microbeam Ca K-edge X-ray absorption near-edge structure spectroscopy (µXANES) indicated that among the forms of CaOx - namely crystalline or amorphous - only amorphous CaOx was present in cod5. These results demonstrate that deletion of COD5 changes both Ca localization and the form of CaOx within leaflets. This article is protected by copyright. All rights reserved.