Improving wheat as a source of iron and zinc for global nutrition

Wheat is the staple food crop in temperate countries and increasingly consumed in developing countries, displacing traditional foods. However, wheat products are typically low in bioavailable iron and zinc, contributing to deficiencies in these micronutrients in countries where wheat is consumed as a staple food. Two factors contribute to the low contents of bioavailable iron and zinc in wheat: the low concentrations of these minerals in white flour, which is most widely consumed, and the presence of phytates in mineral-rich bran fractions. Although high zinc types of wheat have been developed by conventional plant breeding (biofortification), this approach has failed for iron. However, studies in wheat and other cereals have shown that transgenic (also known as genetically modified; GM) strategies can be used to increase the contents of iron and zinc in white flour, by converting the starchy endosperm tissue into a ‘sink’ for minerals. Although such strategies currently have low acceptability, greater understanding of the mechanisms which control the transport and deposition of iron and zinc in the developing grain should allow similar effects to be achieved by exploiting naturally induced genetic variation. When combined with conventional biofortification and innovative processing, this approach should provide increased mineral bioavailability in a range of wheat products, from white flour to wholemeal

Inducing Ni Sensitivity in the Ni Hyperaccumulator Plant Alyssum inflatum Nyárády (Brassicaceae) by Transforming with CAX1, a Vacuolar Membrane Calcium Transporter

The importance of calcium in nickel tolerance was studied in the nickel hyperaccumulator plant Alyssum inflatum by gene transformation of CAX1, a vacuolar membrane transporter that reduces cytosolic calcium. CAX1 from Arabidopsis thaliana with a CaMV35S promoter accompanying a kanamycin resistance gene was transferred into A. inflatum using Agrobacterium tumefaciens. Transformed calli were subcultured three times on kanamycin-rich media and transformation was confirmed by PCR using a specific primer for CAX1. At least 10 callus lines were used as a pool of transformed material. Both transformed and untransformed calli were treated with varying concentrations of either calcium (1–15 mM) or nickel (0– 500 lM) to compare their responses to those ions. Increased external calcium generally led to increased callus biomass, however, the increase was greater for untransformed callus. Further, increased external calcium led to increased callus calcium concentrations. Transformed callus was less nickel tolerant than untransformed callus: under increasing nickel concentrations callus relative growth rate was significantly less for transformed callus. Transformed callus also contained significantly less nickel than untransformed callus when exposed to the highest external nickel concentration (200 lM). We suggest that transformation with CAX1 decreased cytosolic calcium and resulted in decreased nickel tolerance. This in turn suggests that, at low cytosolic calcium concentrations, other nickel tolerance mechanisms (e.g., complexation and vacuolar sequestration) are insufficient for nickel tolerance. We propose that high cytosolic calcium is an important mechanism that results in nickel tolerance by nickel hyperaccumulator plants