Characterization of the Copper Transporters from Lotus spp. and Their Involvement under Flooding Conditions

Forage legumes are an important livestock nutritional resource, which includes essential metals, such as copper. Particularly, the high prevalence of hypocuprosis causes important economic losses to Argentinian cattle agrosystems. Copper deficiency in cattle is partially due to its low content in forage produced by natural grassland, and is exacerbated by flooding conditions. Previous results indicated that incorporation of spp. into natural grassland increases forage nutritional quality, including higher copper levels. However, the biological processes and molecular mechanisms involved in copper uptake by spp. remain poorly understood. Here, we identify four genes that encode putative members of the copper transporter family, denoted COPT in higher plants. A heterologous functional complementation assay of the strain, which lacks the corresponding yeast copper transporters, with the putative COPT proteins shows a partial rescue of the yeast phenotypes in restrictive media. Under partial submergence conditions, the copper content of plants decreases and the expression of two genes is induced. These results strongly suggest that the COPT proteins identified in this work function in copper uptake. In addition, the fact that environmental conditions affect the expression of certain genes supports their involvement in adaptive mechanisms and envisages putative biotechnological strategies to improve cattle copper nutrition.