Iron-dependent halogenases employ cis-halo-Fe(IV)-oxo (haloferryl) complexes to functionalize unactivated aliphatic carbon centers, a capability elusive to synthetic chemists. Halogenation requires (1) coordination of a halide anion (Cl− or Br−) to the enzyme's Fe(II) cofactor; (2) coupled activation of O2 and decarboxylation of α-ketoglutarate to generate the haloferryl intermediate; (3) abstraction of hydrogen (H•) from the substrate by the ferryl oxo group; and (4) transfer of the cis halogen as Cl• or Br• to the substrate radical. This enzymatic solution to an unsolved chemical challenge is potentially generalizable to installation of other functional groups, provided that the corresponding anions can support the four requisite steps. We show here that the wild-type halogenase SyrB2 can indeed direct aliphatic nitration and azidation reactions by the same chemical logic. The discovery and enhancement by mutagenesis of these previously unknown reaction types suggests unrecognized or untapped versatility in ferryl-mediated enzymatic C–H-bond activation.

Crop productivity in semiarid regions is mainly limited by water availability. Root characteristics and plasticity to drought may reduce the negative impact of drought on crop yield. A set of near-isogenic wheat-rye translocation lines was used to test the hypothesis that root system plasticity to drought influences grain yield in wheat. Bread wheat Pavon 76 and 1RS translocation lines, namely Pavon 1RS.1AL, Pavon 1RS.1BL, and Pavon 1RS.1DL were evaluated for root allocation and plasticity in sandtube experiments under well-watered and droughted conditions across 2 years using factorial treatments in a randomized complete block design with four replicates. The 1RS translocation lines had greater root biomass per plant ranging from 7.37 to 8.6 compared to 5.81 g for Pavon 76. Only Pavon 76 showed a positive response to drought by producing more shallow roots (roots developed between 0 and 30 cm) and deep roots (roots developed below 30 cm) in droughted conditions than in well-watered conditions. Thus at drought intensity of 19% (measured as overall reduction in grain yield), grain yield in Pavon 76 was reduced only by 11% compared to the other genotypes with yield reductions ranging from 18 to 24%. However, at drought intensity of 36%, grain yield in Pavon 76 showed maximum reduction indicating that greater root production under drought is advantageous only when plant-available water is enough to support grain production. Grain yield was positively correlated with shallow and deep root weight and root biomass under terminal drought. Correlation coefficients between root system components (shallow and deep root weight and root biomass) and phenological periods were not significant. Our study indicated that genes influencing adaptive phenotypic plasticity of the root system to drought in Pavon 76 are located on chromosome 1BS.

Environmental and economic considerations require the effective use of water and nutrients to elevate grain production in bread wheat (Triticum aestivum L.) with concomitant reduction in nitrate leaching to minimize contamination of underground water. We determined the effect of the root system on leaching fraction, leachate N concentration, and N, P and K uptake using bread wheat ‘Pavon 76’ and its three near‐isogenic translocation lines: Pavon 1RS.1AL, Pavon 1RS.1BL and Pavon 1RS.1DL. These genotypes were grown in sand‐tube experiments under optimum and low level of nutrients for 2 years. Root, stem and leaves, and grain N, P, and K content, and agronomic characters were measured. Leaching fraction and leachate nitrate concentration were measured at early tillering, booting and early grain filling. Significant main effects for year, nutrient level and genotype were found for the characters. Genotype × N interaction was significant only for root P content. Genotype × year interaction was significant only for plant N content, root P content and plant P content. Genotype × year × N interaction was significant only for root N uptake efficiency. Thus, genotypic means averaged across years and nutrient levels are reported. Low levels of nutrients (1330, 235 and 793 mg vs. 1915, 375 and 1268 mg N, P and K, respectively) reduced mean root biomass, plant biomass and grain yield by 27 %, 25 %, and 19 %, respectively. The translocation lines produced 31–46 % more root biomass, 11–14 % heavier grains and 6–8 % greater grain yield than Pavon 76. Leaching fraction was higher under low level of nutrient at booting and grain filling. Leaching fraction at tillering, booting, and grain filling was 67%, 42% and 25%, respectively. Leaching fraction at early tillering was lower for Pavon 1RS.1AL (39 %) and Pavon 1RS.1DL (40.5 %) than for Pavon 76 (45.3 %). Leachate nitrate concentration was lower for two translocation lines at all three stages of plant growth compared to Pavon 76. The correlation coefficient between plant N content and root biomass, between plant N content and plant biomass, and between grain yield and root biomass was positive and significant. Significant positive correlation was found between root biomass and P and K uptake. Multiple small applications of N fertilizer during early plant growth with adequate irrigation water are recommended. Wheat genotypes with superior root characteristics for efficient nutrient uptake, especially during tillering and booting, should be developed in breeding programmes to increase grain yield and to minimize the nitrate leaching.