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The biosynthesis of nitrous oxide in the green alga Chlamydomonas reinhardtii
Author(s) -
Plouviez Maxence,
Wheeler David,
Shilton Andy,
Packer Michael A.,
McLenachan Patricia A.,
SanzLuque Emanuel,
OcañaCalahorro Francisco,
Fernández Emilio,
Guieysse Benoit
Publication year - 2017
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.13544
Subject(s) - chlamydomonas reinhardtii , nitrate reductase , eutrophication , nitrous oxide reductase , environmental chemistry , nitrate , nitrogen cycle , nitrite reductase , nitrite , chlamydomonas , chemistry , nitrogen , biology , biochemistry , ecology , nutrient , organic chemistry , mutant , gene
Summary Over the last decades, several studies have reported emissions of nitrous oxide (N 2 O) from microalgal cultures and aquatic ecosystems characterized by a high level of algal activity (e.g. eutrophic lakes). As N 2 O is a potent greenhouse gas and an ozone‐depleting pollutant, these findings suggest that large‐scale cultivation of microalgae (and possibly, natural eutrophic ecosystems) could have a significant environmental impact. Using the model unicellular microalga Chlamydomonas reinhardtii , this study was conducted to investigate the molecular basis of microalgal N 2 O synthesis. We report that C. reinhardtii supplied with nitrite ( NO 2 − ) under aerobic conditions can reduce NO 2 − into nitric oxide ( NO ) using either a mitochondrial cytochrome c oxidase ( COX ) or a dual enzymatic system of nitrate reductase ( NR ) and amidoxime‐reducing component, and that NO is subsequently reduced into N 2 O by the enzyme NO reductase ( NOR ). Based on experimental evidence and published literature, we hypothesize that when nitrate ( NO 3 − ) is the main Nitrogen source and the intracellular concentration of NO 2 − is low (i.e. under physiological conditions), microalgal N 2 O synthesis involves the reduction of NO 3 − to NO 2 − by NR followed by the reduction of NO 2 − to NO by the dual system involving NR . This microalgal N 2 O pathway has broad implications for environmental science and algal biology because the pathway of NO 3 − assimilation is conserved among microalgae, and because its regulation may involve NO .