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<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background and aims</jats:title> <jats:p><jats:italic>Sinorhizobium fredii</jats:italic> HH103 is a broad host-range rhizobial strain able to induce the formation of nitrogen-fixing nodules in dozens of legumes, including soybean. <jats:italic>S. fredii</jats:italic> HH103 exhibits genistein-induced surface motility. The aim of this work has been to determine whether the <jats:italic>flgJ</jats:italic> gene, which is inducible by genistein and codes for a flagellar protein, is involved in this motility and is relevant for symbiosis with soybean.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>We have generated two independent mutants in the <jats:italic>flgJ</jats:italic> gene of HH103 and analysed their phenotypes in motility, exopolysaccharide production, biofilm formation, soybean root colonization, symbiosis with soybean, and secretion of effector proteins. We have also further studied the regulation of the expression of <jats:italic>flgJ</jats:italic>.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>We show that the expression of <jats:italic>flgJ</jats:italic> is driven by a <jats:italic>tts</jats:italic> box previously not detected, which accounts for its induction by flavonoids and the NodD1 and TtsI transcriptional activators. Inactivation of <jats:italic>flgJ</jats:italic> led to severe impairments in bacterial motility (swimming and genistein-induced surface motility) as well as to a significant reduction in symbiotic performance with soybean when bacteria are not directly inoculated onto the seedling roots. However, the absence of a functional FlgJ protein did not affect the bacterial ability to colonize soybean roots.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusion</jats:title> <jats:p>The <jats:italic>flgJ</jats:italic> gene of <jats:italic>S. fredii</jats:italic> HH103 connects the <jats:italic>nod</jats:italic> regulon with the genistein-induced surface motility exhibited by this rhizobial strain.</jats:p> </jats:sec>

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background and Aims</jats:title> <jats:p>Methane (CH<jats:sub>4</jats:sub>) fluxes at peatland plant surfaces are net results of transport of soil-produced CH<jats:sub>4</jats:sub> and within-plant CH<jats:sub>4</jats:sub> production and consumption, yet factors and processes controlling these fluxes remain unclear. We aimed to assess the effects of seasonality, environmental variables, and CH<jats:sub>4</jats:sub> cycling microbes on CH<jats:sub>4</jats:sub> fluxes from characteristic fen species.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>Four species (<jats:italic>Carex rostrata</jats:italic>, <jats:italic>Menyanthes trifoliata</jats:italic>, <jats:italic>Betula nana</jats:italic>, <jats:italic>Salix lapponum</jats:italic>) were selected, and their CH<jats:sub>4</jats:sub> fluxes determined in climate-controlled environments with three mesocosms per growing season per species. Microbial genes for CH<jats:sub>4</jats:sub> cycling were analysed to check the potential for within-plant CH<jats:sub>4</jats:sub> production and oxidation. Two extra experiments were conducted: removal of <jats:italic>C. rostrata</jats:italic> leaves to identify how leaves constrain CH<jats:sub>4</jats:sub> transport, and a labelling experiment with <jats:italic>S. lapponum</jats:italic> to distinguish between plant-produced and soil-produced CH<jats:sub>4</jats:sub> in the plant flux.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>All species showed seasonal variability in CH<jats:sub>4</jats:sub> fluxes. Higher porewater CH<jats:sub>4</jats:sub> concentration increased fluxes from <jats:italic>C. rostrata</jats:italic> and <jats:italic>M. trifoliata</jats:italic>, decreased fluxes from <jats:italic>S. lapponum</jats:italic>, and did not affect fluxes from <jats:italic>B. nana</jats:italic>. Air temperature only and negatively affected CH<jats:sub>4</jats:sub> flux from <jats:italic>C. rostrata</jats:italic>. Light level did not impact CH<jats:sub>4</jats:sub> fluxes. Both methanogens and methanotrophs were detected in shoots of <jats:italic>S. lapponum</jats:italic> and <jats:italic>M. trifoliata</jats:italic>, methanotrophs in <jats:italic>B. nana</jats:italic>, and neither in <jats:italic>C. rostrata</jats:italic>.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusion</jats:title> <jats:p>Our study demonstrates that the seasonal phase of the plants regulates the CH<jats:sub>4</jats:sub> fluxes they mediate across species. The detection of methanogens and methanotrophs in herbs and shrubs suggests that microbial processes may contribute to their CH<jats:sub>4</jats:sub> fluxes.</jats:p> </jats:sec>