title: Is vanadium a biometal for boreal cyanolichens?
abstract: Molybdenum (Mo) nitrogenase has long been considered the predominant isoenzyme responsible for dinitrogen fixation worldwide. Recent findings have challenged the paradigm of Mo hegemony, and highlighted the role of alternative nitrogenases, such as the vanadium-nitrogenase. Here, we first characterized homeostasis of vanadium (V) along with other metals in situ in the dinitrogen fixing cyanolichen Peltigera aphthosa. These lichens were sampled in natural sites exposed to various levels of atmospheric metal deposition. These results were compared with laboratory experiments where Anabaena variabilis, which is also hosting the V-nitrogenase, and a relatively close relative of the lichen cyanobiont Nostoc, was subjected to various levels of V. We report here that V is preferentially allocated to cephalodia, specialized structures where dinitrogen fixation occurs in tri-membered lichens. This specific allocation is biologically controlled and tightly regulated. Vanadium homeostasis in lichen cephalodia exposed to various V concentrations is comparable to the one observed in Anabaena variabilis and other dinitrogen fixing organisms using V-nitrogenase. Overall, our findings support current hypotheses that V could be a more important factor in mediating nitrogen input in high latitude ecosystems than previously recognized. They invite the reassessment of current theoretical models linking metal dynamics and dinitrogen fixation in boreal and subarctic ecosystems.
authors.affiliation: Centre Sève, Département de chimie, Université de Sherbrooke, J1K 2R1, QC, Canada.
authors.forename: Romain
authors.initials: R
authors.lastname: Darnajoux
authors.affiliation: Centre Sève, Département de chimie, Université de Sherbrooke, J1K 2R1, QC, Canada.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Constantin
authors.affiliation: Department of Biology, Duke University, Box 90338, Durham, NC, 27708-0338, USA.
authors.forename: Jolanta
authors.initials: J
authors.lastname: Miadlikowska
authors.affiliation: Department of Biology, Duke University, Box 90338, Durham, NC, 27708-0338, USA.
authors.forename: François
authors.initials: F
authors.lastname: Lutzoni
authors.affiliation: Centre Sève, Département de chimie, Université de Sherbrooke, J1K 2R1, QC, Canada.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Bellenger
mesh_terms: D017033:Anabaena / Q000166:cytology / Q000187:drug effects; D008011:Lichens / Q000187:drug effects / Q000378:metabolism*; D011792:Quebec; D014025:Titanium / Q000378:metabolism; D014639:Vanadium / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D014639:Vanadium; D014025:Titanium
keywords: boreal ecosystems; cyanolichens; dinitrogen fixation; homeostasis; metals; vanadium (V)