Urease deficiency alters nitrogen metabolism and gene expression in urease-null soybean without affecting growth or productivity under nitrate supply

Author(s)

Ribeiro de Souza, Sarah Caroline ^{[1, 2]} ; Sodek, Ladaslav ^[2] ; Polacco, Joe Carmine ^[3] ; Mazzafera, Paulo ^{[2, 4]}

Affiliation

^[1] Univ Fed Sao Carlos, Dept Bot, POB 676, BR-13565905 Sao Carlos, SP - Brazil

^[2] Univ Estadual Campinas, Inst Biol, Dept Plant Biol, POB 6109, BR-13083970 Campinas, SP - Brazil

^[3] Univ Missouri, Dept Biochem, Interdisciplinary Plant Grp, 117 Schweitzer Hall, Columbia, MO 65211 - USA

^[4] Univ Sao Paulo, Coll Agr Luiz de Queiroz, Dept Crop Sci, CP 09, BR-13418900 Piracicaba, SP - Brazil

• Document type: Journal article
• Source: ACTA PHYSIOLOGIAE PLANTARUM; v. 42, n. 3 FEB 13 2020.
• Web of Science Citations: 0

Abstract

Urea is a product of arginine catabolism in plants and its Nitrogen is recycled into the plant metabolism as ammonium after hydrolysis by urease. The eu3-a soybean mutant is null for the Ni insertion protein (UreG) necessary for urease activity. No UreG protein nor any activity of the urease enzymes is detectable in these eu3-a mutants. In order to understand the mechanisms of nitrogen cycling in soybean and the possible physiological benefits to N metabolism, eu3-a (urease-null) and control soybean near-isogenic Eu3 plants were studied. They were grown to two different developmental stages (vegetative-V5 and reproductive-R5) with 15 mM nitrate as the sole source of nitrogen. Growth and biochemical parameters (such as amino acid, nitrate, and polyamine pools) were evaluated in leaves. Gene transcript levels were determined for some enzymes related to Arg catabolism, together with those of the DUR3 active urea transporter and the UreG Ni-insertion accessory protein, whose transcript was confirmed to be absent in eu3-a. The absence of urease activity in the eu3-a null plants did not affect growth or yield although there was a substantial and progressive accumulation of urea in the leaves. Metabolic changes occurred mainly in the pool of amino acids and in the expression of genes related to the pathway of Arg degradation. There are indications that the pathway may be diverted to form polyamines, but to a limited extent. Thus, considering both developmental stages, the degradation of Arg to urea and Orn remains the main path for nitrogen recycling from Arg, despite the progressive accumulation of urea and consequently immobilization of N. (AU)

• FAPESP's process: 08/58035-6 - Control of lignin biosynthesis in sugar cane: many gaps still to be filled
• Grantee: Paulo Mazzafera
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Thematic Grants
• FAPESP's process: 13/25094-8 - Evaluation of the nitrogen cycling in soybean mutants eu3-a (urease-negative) and non-mutant using nitrate or N2 from biological fixation as nitrogen sources
• Grantee: Sarah Caroline Ribeiro de Souza
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/09730-4 - Urease in the metabolism of nitrogen in plants and its relationship with Ni as a nutrient
• Grantee: Paulo Mazzafera
• Support Opportunities: Research Grants - Visiting Researcher Grant - International