Nutritional impact of elevated calcium transport activity in carrots

Jeon

Proc. Natl. Acad. Sci. U.S.A.

et al. 2009

309

246

The most widespread dietary problem in the world is mineral deficiency. We used the nicotianamine synthase (NAS) gene to increase mineral contents in rice grains. Nicotianamine (NA) is a chelator of metals and a key component of metal homeostasis. We isolated activation-tagged mutant lines in which expression of a rice NAS gene, OsNAS3, was increased by introducing 35S enhancer elements. Shoots and roots of the OsNAS3 activationtagged plants (OsNAS3-D1) accumulated more Fe and Zn. Seeds from our OsNAS3-D1 plants grown on a paddy field contained elevated amounts of Fe (2.9-fold), Zn (2.2-fold), and Cu (1.7-fold). The NA level was increased 9.6-fold in OsNAS3-D1 seeds. Analysis by size exclusion chromatography coupled with inductively coupled plasma mass spectroscopy showed that WT and Os-NAS3-D1 seeds contained equal amounts of Fe bound to IP6, whereas OsNAS3-D1 had 7-fold more Fe bound to a low molecular mass, which was likely NA. Furthermore, this activation led to increased tolerance to Fe and Zn deficiencies and to excess metal (Zn, Cu, and Ni) toxicities. In contrast, disruption of OsNAS3 caused an opposite phenotype. To test the bioavailability of Fe, we fed anemic mice with either engineered or WT seeds for 4 weeks and measured their concentrations of hemoglobin and hematocrit. Mice fed with engineered seeds recovered to normal levels of hemoglobin and hematocrit within 2 weeks, whereas those that ate WT seeds remained anemic. Our results suggest that an increase in bioavailable mineral content in rice grains can be achieved by enhancing NAS expression. activation tagging ͉ bioavailability ͉ hemoglobin ͉ metal homeostasis

Section: Discussionmentioning

confidence: 99%

Iron fortification of rice seeds through activation of the nicotianamine synthase gene

Jeon

Proc. Natl. Acad. Sci. U.S.A.

et al. 2009

309

246

“…Using stable isotope labelling methods and human subjects the CAX‐enhanced carrots appear to contain more bioavailable Ca 2+ (Morris et al . 2008). Furthermore, using a panel of taste testers, CAX expressing lettuce varieties appear to have retained their taste and texture qualities (Park et al .…”

Section: The Cax Transporters In Biotechnologymentioning

confidence: 99%

CAX‐ing a wide net: Cation/H⁺ transporters in metal remediation and abiotic stress signalling

2016

Cation/proton exchangers (CAXs) are a class of secondary energised ion transporter that are being implicated in an increasing range of cellular and physiological functions. CAXs are primarily Ca2+ efflux transporters that mediate the sequestration of Ca2+ from the cytosol, usually into the vacuole. Some CAX isoforms have broad substrate specificity, providing the ability to transport trace metal ions such as Mn2+ and Cd2+, as well as Ca2+. In recent years, genomic analyses have begun to uncover the expansion of CAXs within the green lineage and their presence within non‐plant species. Although there appears to be significant conservation in tertiary structure of CAX proteins, there is diversity in function of CAXs between species and individual isoforms. For example, in halophytic plants, CAXs have been recruited to play a role in salt tolerance, while in metal hyperaccumulator plants CAXs are implicated in cadmium transport and tolerance. CAX proteins are involved in various abiotic stress response pathways, in some cases as a modulator of cytosolic Ca2+ signalling, but in some situations there is evidence of CAXs acting as a pH regulator. The metal transport and abiotic stress tolerance functions of CAXs make them attractive targets for biotechnology, whether to provide mineral nutrient biofortification or toxic metal bioremediation. The study of non‐plant CAXs may also provide insight into both conserved and novel transport mechanisms and functions.

Proc. Natl. Acad. Sci. U.S.A.

“…One matter that needs to be considered is the bioavailability of the enhanced vitamins. In most micronutrient-enhanced plants reported to date, assumptions about whether the nutrients can be readily absorbed by humans have not been tested (24), although there are examples in which absorption studies have been carried out with mice and humans to show the direct nutritional benefits of mineral-enhanced crops (25).…”

Section: Potential Nutritional Impact Of Multivitamin Biofortified Cornmentioning

confidence: 99%

Transgenic multivitamin corn through biofortification of endosperm with three vitamins representing three distinct metabolic pathways

Naqvi

Zhu

Farré

et al. 2009

449

310

Vitamin deficiency affects up to 50% of the world's population, disproportionately impacting on developing countries where populations endure monotonous, cereal-rich diets. Transgenic plants offer an effective way to increase the vitamin content of staple crops, but thus far it has only been possible to enhance individual vitamins. We created elite inbred South African transgenic corn plants in which the levels of 3 vitamins were increased specifically in the endosperm through the simultaneous modification of 3 separate metabolic pathways. The transgenic kernels contained 169-fold the normal amount of ␤-carotene, 6-fold the normal amount of ascorbate, and double the normal amount of folate. Levels of engineered vitamins remained stable at least through to the T3 homozygous generation. This achievement, which vastly exceeds any realized thus far by conventional breeding alone, opens the way for the development of nutritionally complete cereals to benefit the world's poorest people.folic acid ͉ metabolic engineering ͉ transgenic maize ͉ vitamin A fortification ͉ vitamin C