A novel nitrous oxide mitigation strategy: expressing nitrous oxide reductase fromPseudomonas stutzeriin transgenic plants

Wan, S., Greenham, T., Goto, K., Mottiar, Y., Johnson, A. M., Staebler, J. M., Zaidi, M. A., Shu, Q. and Altosaar, I. 2014. A novel nitrous oxide mitigation strategy: expressing nitrous oxide reductase from Pseudomonas stutzeri in transgenic plants. Can. J. Plant Sci. 94: 1013–1025. As a stable greenhouse gas, nitrous oxide (N2O) plays a significant role in stratospheric ozone destruction. The primary anthropogenic N2O source is the use of nitrogen in agriculture. Currently, the annual N2O emissions from this soil–plant–microbial system is more than 2.6 Tg (1 Tg=1 million metric tonnes) of N2O-N globally. So it is important to explore some innovative and effective biology-based strategies for N2O mitigation. If shown to be effective in field trails as well as laboratory-scale experiments, such GMO plants could help guide international policies on adaptation to climate change. The bacterial enzyme nitrous oxide reductase (N2OR) is the only known enzyme capable of catalyzing the final step of the denitrification pathway, conversion of N2O to N2. To “scrub” the N2O emissions, bacterial N2OR was heterologously expressed in plants. Structurally, the enzyme N2OR is encoded by nosZ, but its biosynthesis and assembly in prokaryotes require the products of several nos genes, including a putative ABC-type transporter encoded by nosDFY, and the copper chaperone NosL for biogenesis of the metal centre. We have generated transgenic tobacco plants expressing the nosZ gene, as well as tobacco plants in which the other nos genes were co-expressed under the control of a root-specific promoter (rolD) and a constitutive promoter (d35S). The nosZ gene from Pseudomonas stutzeri heterologously expressed in tobacco produced active recombinant N2OR. The positive results in the preliminary proof-of-principle experiments indicated that plants heterologously expressing N2OR could mitigate emissions at the source before N2O reaches the stratosphere or troposphere.