The concentrations and distribution of phytic acid-phosphorus and other mineral nutrients in wild-type andlow phytic acid1-1 (lpa1-1) corn (Zea maysL.) grains and grain parts

Abstract

A comparison of mineral nutrient and phytic acid-phosphorus (PA-P) distribution in the grains of wild-type (WT) and low phytic acid1-1 (lpa1-1) corn (Zea mays L.) was conducted to determine how the lpa1-1 mutation influences mineral element concentrations in different grain parts and impacts the structure of phosphorus-rich inclusions (globoids) in the grain cells. This is the first report regarding total phosphorus (P) and PA-P concentrations in scutellum and root-shoot axis portions of cereal embryos of WT in comparison to its matching lpa1-1 genotype. In WT, 95% of the grain PA-P was located in the embryo, mostly in the scutellum. The lpa1-1 mutation reduced whole-grain PA-P by 62% but influenced the scutella more than the root-shoot axes and rest-of-grain fractions. In spite of the lpa1-1 mutants containing greatly reduced PA-P, whole-grain amounts of Mg, Fe, and Mn were higher in lpa1-1 than in WT, K and Zn were similar, and Ca was lower. Iron was 1/3 higher in lpa1-1 grains than WT while Ca was 18% lower. Decreased phytic acid in lpa1-1 grains resulted in reduction in globoid size in both scutellum and aleurone layer cells. Most lpa1-1 aleurone globoids were non-spherical and scutellum globoids were clusters of small spheres while WT globoids were large discrete spheres. X-ray analyses of globoids in both grain types revealed major amounts of P, K, and Mg and traces of Ca, Fe, and Zn. Both grain types contained almost no mineral nutrient stores in the starchy endosperm.Key words: corn (Zea mays L.), phytic acid-phosphorus, low phytic acid1-1 (lpa1-1) grains, mineral nutrients, globoids, electron microscopy.

Dynamic Changes in the Distribution of Minerals in Relation to Phytic Acid Accumulation during Rice Seed Development

“…However, in these studies, Cu and Zn may have had a high affinity for InsP 6 . In contrast to these in vitro results, in vivo InsP 6 is stored mainly with Mg and K in rice and corn (Zea mays) seeds (Ogawa et al, 1975;Lin et al, 2005) and with Mg, K, and Ca in wheat (Triticum aestivum) seeds (Bohn et al, 2007). In this study, m-XRF analysis at a 1-mm step size also indicated that Ca, K, and Fe bind strongly to phytic acid, Zn binds loosely, and Cu scarcely binds to phytic acid.…”

A decrease in phytic acid content substantially affects the distribution of mineral elements within rice seeds

“…During seed development, the aleurone cells are gradually filled with globoids and oil bodies, and therefore, metal elements that do not form phytate salt will be gradually extruded from the aleurone layer to the endosperm. A reduction in globoid size was observed in the aleurone layer of lpa seeds in rice, barley, and corn [32,35,36]. Because the estimated width of the aleurone layers of the two lpa mutants were similar to that of WT, it is plausible that Zn and Cu in the lpa seeds were not moved out into the endosperm, but remained in the spaces between small globoids in the aleurone layer.…”

Assessment of the contents of phytic acid and divalent cations in low phytic acid (lpa) mutants of rice and soybean

“…Results obtained for maize (Lin et al, 2005), barley (Liu et al, 2007a) and wheat (Guttieri et al, 2006) indicated that lpa mutations do not result in systematic increases or decreases of the mineral contents in these crops.…”