Opinion: nickel and urease in plants: still many knowledge gaps.

Plant science : an international journal of experimental plant biology (2012-12-26)
Joe C Polacco, Paulo Mazzafera, Tiago Tezotto
ABSTRACT

We propose experimental strategies to expand our understanding of the role of Ni in plants, beyond the Ni-metallocenter of urease, still the only identified Ni-containing plant enzyme. While Ni has been considered an essential mineral for plants there is a clear lack of knowledge of its involvement in metabolic steps except the urease-catalyzed conversion of urea to ammonia and bicarbonate. We argue that urease (and hence, Ni) plays an important role in optimal N-use efficiency under various N regimes by recycling urea-N, which is generated endogenously exclusively from arginase action on arginine. We further suggest that urease and arginase may connect different metabolic compartments under stress situations, and therefore may be involved in stress tolerance. To determine possible non-urease roles of Ni we call for experimental manipulation of both Ni and N availability in urease-negative mutants. Plant ureases have been shown to have defense roles, distinct from their ureolytic activity, and we call for investigation of whether Ni helps maintain a urease conformation or stability for these non-ureolytic defense roles. The beneficial effects of Ni at upper concentration limits have not been fully examined. We posit a "Ni strategy" of plants whose growth/performance is stimulated by unusual amounts of soil Ni, for defense and/or for maximal N-use efficiency. While we know little about Ni and urease roles in N metabolism and defense, virtually nothing is known about Ni roles in plant-microbial 'consortia.' And, much of what we know of Ni and urease is limited to only a few plants, e.g. soybean, potato and Arabidopsis, and we suggest studies vigorously extended to other plants.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Raney®-Nickel, W.R. Grace and Co. Raney® 2800, slurry, in H2O, active catalyst
Sigma-Aldrich
Urease from Canavalia ensiformis (Jack bean), Type III, powder, 15,000-50,000 units/g solid
Sigma-Aldrich
Nickel, nanopowder, <100 nm avg. part. size, ≥99% trace metals basis
Sigma-Aldrich
Urease from Canavalia ensiformis (Jack bean), Type C-3, powder, ≥600,000 units/g solid
Sigma-Aldrich
Urease from Canavalia ensiformis (Jack bean), Type IX, powder, 50,000-100,000 units/g solid
Sigma-Aldrich
Urease from Canavalia ensiformis (Jack bean), Type III, glycerol solution, 500-800 units/mL
Sigma-Aldrich
Urease from Canavalia ensiformis (Jack bean)
Sigma-Aldrich
Urease from Canavalia ensiformis (Jack bean), powder, ~1 U/mg
Sigma-Aldrich
Nickel, foil, thickness 0.125 mm, ≥99.9%
Sigma-Aldrich
Nickel, powder, <150 μm, 99.99% trace metals basis
Sigma-Aldrich
Urease from Canavalia ensiformis (Jack bean), powder, white, ~8 U/mg
Sigma-Aldrich
Raney®-Nickel, W.R. Grace and Co. Raney® 2400, slurry, in H2O, active catalyst
Sigma-Aldrich
Nickel, foil, thickness 0.5 mm, 99.98% trace metals basis
Sigma-Aldrich
Nickel, wire, diam. 0.25 mm, ≥99.9%
Sigma-Aldrich
Nickel, foil, thickness 0.1 mm, 99.98% trace metals basis
Sigma-Aldrich
Nickel, wire, diam. 0.5 mm, ≥99.9% trace metals basis
Sigma-Aldrich
Nickel, wire, diam. 0.5 mm, ≥99.99% trace metals basis
Sigma-Aldrich
Nickel, rod, diam. 6.35 mm, ≥99.99% trace metals basis
Sigma-Aldrich
Nickel, foil, thickness 0.25 mm, 99.995% trace metals basis
Nickel, mesh, 100x250mm, nominal aperture 0.73mm, wire diameter 0.25mm, 26x26 wires/inch, open area 55%, plain weave mesh, 99%
Nickel, wire reel, 20m, diameter 0.025mm, as drawn, 99.98%
Nickel, wire reel, 10m, diameter 0.01mm, as drawn, 99.98%
Nickel, rod, 100mm, diameter 16mm, 99.99+%
Nickel, foil, not light tested, 100x100mm, thickness 0.01mm, 99.95%
Nickel, wire reel, 20m, diameter 0.125mm, hard, 99.98%
Nickel, rod, 100mm, diameter 3.0mm, 99%
Nickel, wire reel, 1m, diameter 1.0mm, hard, 99.98%
Nickel, broken cathode squares, 1000g, max. size 50mm, 99.8%
Nickel, tube, 1000mm, outside diameter 6.5mm, inside diameter 5.5mm, wall thickness 0.5mm, hard, 99.5%
Nickel, foil, 50mm disks, thickness 0.05mm, annealed, 99%