Jokipii-Lukkari S Kastaniotis AJ Parkash V Sundström R Leiva-Eriksson N Nymalm Y Blokhina O Kukkola E Fagerstedt KV Salminen TA Läärä E Bülow L Ohlmeier S Hiltunen JK Kallio PT Häggman H 2016 Previous reports have connected non-symbiotic and truncated hemoglobins (Hbs) to metabolism of nitric oxide (NO), an important signalling molecule involved in wood formation. We have studied the capability of poplar (Populus tremula × tremuloides) Hbs PttHb1 and PttTrHb proteins alone or with a flavin-protein reductase to relieve NO cytotoxicity in living cells. Complementation tests in a Hb-deficient, NO-sensitive yeast (Saccharomyces cerevisiae) Δyhb1 mutant showed that neither PttHb1 nor PttTrHb alone protected cells against NO. To study the ability of Hbs to interact with a reductase, ferredoxin NADP(+) oxidoreductase PtthFNR was characterized by sequencing and proteomics. To date, by far the greatest number of the known dual-targeted plant proteins are directed to chloroplasts and mitochondria. We discovered a novel variant of hFNR that lacks the plastid presequence and resides in cytosol. The coexpression of PttHb1 and PtthFNR partially restored NO resistance of the yeast Δyhb1 mutant, whereas PttTrHb coexpressed with PtthFNR failed to rescue growth. YFP fusion proteins confirmed the interaction between PttHb1 and PtthFNR in plant cells. The structural modelling results indicate that PttHb1 and PtthFNR are able to interact as NO dioxygenase. This is the first report on dual targeting of central plant enzyme FNR to plastids and cytosol. https://sonar.ch/global/documents/36598 eng info:eu-repo/semantics/altIdentifier/doi/10.1016/j.plantsci.2016.03.013 info:eu-repo/semantics/altIdentifier/pmid/27095407 Plant science : an international journal of experimental plant biology. - 2016 Dioxygenation Dual targeting Ferredoxin NADP(+) oxidoreductase Hemoglobin Nitric oxide Poplar Chloroplasts Cytosol Ferredoxin-NADP Reductase Genes, Reporter Hemoglobins Mitochondria Mutation Nitric Oxide Oxygenases Plant Proteins Populus Proteomics Recombinant Fusion Proteins Saccharomyces cerevisiae Sequence Analysis, DNA Dual targeted poplar ferredoxin NADP(+) oxidoreductase interacts with hemoglobin 1. http://purl.org/coar/resource_type/c_6501