Iron transporter research may deliver higher-nutrient crops
the soil could make it possibly to engineer higher-yield,
nutrient-rich crops in poor quality soils and increase biomass in
soils currently under cultivations, claim US scientists.
Deficiencies of the micronutrients iron and zinc can limit plant growth and affect yield volumes - and also have an effect on the health of consumers who rely on them for nourishment.
At a meeting of the American Society of Plant Biologists in Boston, Professor Mary Lou Guerinot of Dartmouth University will today present her solution to the problem: the engineering of plants to be better sources of essential nutrients such as iron.
Professor Guerinot and colleagues had previously identified the transporter IRT1 as being responsible for the uptake of iron from the soil, but it seems some plants may have lost this function in modern environments.
The problem is, however, that IRT1 also transports other metals such as manganese, zinc, cobalt and cadmium - and cadmium is an undesirable metal in foodstuffs since it is extremely toxic and can accumulate in and cause damage to the internal organs.
This problem is compounded, says Guerinot, by the use of phosphate fertilizers, which has led to high levels of cadmium contamination in many locations around the world.
In her presentation, Guerinot explains how she and her team used DNA shuffling and herterologous expression in yeast to isolate alleles (DNA sequences) of IRT1, which allow the iron to be transported but not the cadmium.
She tested the efficacy of the method by comparing the cadmium levels in the transgenic seedlings with those of plants that have lost their IRT1 function, and found them to be the same.
Moreover, the tests showed up another benefit: the transgenic plants were seen to have twice as much iron as the wild type plants, when grown in the presence of cadmium.
In particular, increasing levels of iron in rice - a staple in many poor countries - could help tackle deficiencies, which can lead to anaemia and impairment of mental development. According to the United Nations World Food Programme, iron deficiency is the most common form of malnutrition, affecting 4.5 billion people worldwide. It is estimated to impair the mental development of 40-60 percent children in developing countries.
More than the health impact, the WFP also says that widespread iron deficiency damages productivity and can cut GDP by as much as two percent in some countries.
The next phase of Prof Guerinot's team's work is expected to "aid the development of nutrient-rich seed, beneficially affecting human nutrition and health," she said.
The researchers have already begun looking at the distribution of the metals within the plant organs and seed, using X-ray fluorescent microtomography. So far they have looked at Arabidopsis (rockcress) seed in vivo, to see which transporters affect the distribution of misrocnutrients within it.
"This research should also lead to agronomic benefits such as increased seedling vigour, higher crop yields and resistance to disease."
