Legume grains have an important socio-economical role, being highly utilized in human and animal nutrition. They are mainly cultivated for their edible seeds, sources of micronutrients, and their high protein content. Although iron (Fe) is the fourth most abundant element in the earth’s crust, its limited solubility makes it poorly bioavailable for plants, lowering the Fe content of their seeds. In poorer countries, where seeds are the main components of their diets, the access to diverse food sources and fortified food sources is often limited, increasing the prevalence of several diseases associated with undernourishment, namely Iron Deficiency Anemia (IDA). Various strategies are being used to withstand this disease and one of them is biofortification. However, to increase the seeds mineral content, one must understand the mechanisms underlying the minerals pathway to the plants edible parts. Thus, Fe related genes involved in nutrient uptake (FRO2, IRT1), transport (NRAMP3, VIT1, YSL1), and storage (Ferritin), as well as novel candidate genes (GCN2 and WEE1), were studied, in two significant crops utilized in human and animal nutrition: Glycine max and Medicago sp. This work also focused on the common physiological mechanisms underlying the response to Fe deficiency, of these two species, grown under Fe-deficient and Fe-sufficient conditions. In the current work, both species were very susceptible to Iron Deficiency Chlorosis (IDC), developing several characteristic symptoms, such as yield reduction, yellowing of leaves and development of secondary roots. Fe acquisition genes, FRO2 and IRT1, presented similar expression patterns, suggesting that IRT1 is co-regulated with FRO2. In what concerns Fe transport, NRAMP3 and VIT1, showed opposite functions and appeared to have a stronger expression in the leaves. YSL1 and Ferritin presented higher expression levels under Fe-sufficient conditions in shoots and roots. The results obtained for GCN2 strongly indicate that this gene plays a role in Fe metabolism, since in the lack of Fe it is over-expressed, mainly in roots. In what concerns to WEE1, the results show that this gene seems to have a more important role in Fe-sufficient roots, being under-expressed in stress situations, where growth is diminished. When submitted to stress conditions, both species presented a similar nutritional impact, with a decreased nutrient content, where Zn predominates in the aerial part, whereas Fe predominates in the roots. This work contributes to an enhanced understanding, on Fe deficiency response mechanisms, as well as new Fe-metabolism related genes, crucial not only to combat IDC crop devastation and consequent economic damage, but also to increase Fe content in the edible parts of legume plants in order to improve human nutrition and health.
- Mestrado em Engenharia Alimentar
Evaluation of the physiological and molecular impact of iron deficiency in two legume species
Mendes, I. V. S. B. (Student). 2014
Student thesis: Master's Thesis