We take a multi-faceted approach towards crop biofortification. Our research focuses on how plants absorb nutrients as well as the factors affecting nutrient bioavailability in edible parts of plants. We are also interested in understanding the nutrient decreases that occur under elevated carbon dioxide and determining if certain biofortification strategies can counteract those decreases. Our biofortification research can be broken down into three major themes:
- Nutrient uptake and transport – plants use a variety of molecules to mobilize iron (Fe) and zinc (Zn) in plant tissues and to absorb these nutrients from soil. A key molecule underpinning Fe and Zn movement in all higher plants is nicotianamine, a non-protein amino acid that chelates and solubilizes transition metals. We have produced Fe and Zn biofortified rice and wheat through constitutive expression of the rice nicotianamine synthase 2 (OsNAS2) gene. We have also discovered that wheat has at least 21 NAS genes in its large, hexaploid genome. Read more – Johnson et al. 2011, Kyriacou et al. 2014, Bonneau et al. 2016, Beasley et al. 2019.
- Nutrient bioavailability – the bioavailability of plant-derived Fe and Zn in human diets is influenced by the molecules that these nutrients associate with in plant tissues. Phytic acid is a storage molecule in plant seeds that often binds to Fe and Zn and creates insoluble complexes that humans are unable to digest. Our research indicates that nicotianamine, rather than phytic acid, is preferentially bound to increased Fe in NAS biofortified rice and wheat and that these nicotianamine-Fe complexes are highly bioavailable in human diets. We are also exploring the role that ascorbic acid (vitamin C), a powerful antioxidant and enhancer of Fe bioavailability, can play in our biofortification research. Read more – Trijatmiko et al. 2016, Macknight et al. 2017.
- Nutrition and climate change – The Earth’s atmospheric carbon dioxide concentration is expected to reach at least 550 ppm CO2 by 2050. This represents a large increase from today’s concentration of 410 ppm CO2 and will have major effects on the growth and physiology of terrestrial plants. Numerous studies have demonstrated that Fe and Zn concentrations significantly decrease in C3 grains and legumes under the atmospheric carbon dioxide concentrations predicted for 2050. We are analysing Fe and Zn dynamics in rice and wheat plants under ambient and elevated CO2 to uncover why these nutritional decreases occur, and to pinpoint strategies that may help counteract them. Read more – Johnson 2013.