Analysis of urea assimilation in Vriesea gigantea (Bromeliaceae) plants with low urease activity: is mandatory the urea hydrolysis for its assimilation?

• Grant number: 15/23210-6
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: April 15, 2016
• End date: June 26, 2016
• Field of knowledge: Biological Sciences - Botany - Pant Physiology
• Principal Investigator: Helenice Mercier
• Grantee: Alejandra Matiz Lopez
• Supervisor: Torgny Nasholm
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Swedish University of Agricultural Sciences, Uppsala (SLU), Sweden
• Associated to the scholarship: 13/09097-7 - Characterization of the absorption of urea via aquaporins and its possible direct assimilation by Vriesea gigantea (Bromeliaceae), BP.DR

Abstract

Organic molecules can be the main input of nitrogen for plants in environments where inorganic nitrogen sources are limited, such as epiphytic habitat. Recent studies conducted in our laboratory at IBUSP have shown a high capacity of Vriesea gigantea plants to absorb urea by their leaves, making this bromeliad an excellent model to study urea metabolism. Nevertheless, urea uptake and assimilation processes are little characterized in these plants. It was suggested that after urea absorption, this organic N compound is previously hydrolyzed by urease enzyme into CO2 and NH4+ in order to be assimilated. However, considering the high efficiency for urea absorption by V. gigantea, we believe that in some cases urea assimilation into amino acids might occur by other pathway, independent of urease activity. This alternative pathway, although not the main one, might be important in the early moments of urea absorption when this source is available in high concentrations. Therefore, urease relevance in urea assimilation process will be investigated through the analysis of the amino acid profile in V. gigantea plants kept under urease inhibitor and supplied with labeled [13C]-[15N]-urea, since under a situation where urease activity is insufficient, urea could be assimilated directly into organic compounds. Urea assimilation experiments will be conducted in young and adult ontogenetic stages of V. gigantea due to their metabolic and morphological differences. (AU)