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<p>Biological nitrogen fixation (BNF) as the primarily nitrogen supply for rice growth has lately been linked to Fe(III) reduction in paddy field. Rice root iron plaque (IP) is crucial in rhizosphere elements cycling and retaining pollutants, but the synergistic interaction between rhizospheric Fe cycle and BNF remains elusive. Herein, rice seedlings with and without IP on rice root were cultured under hydroponic conditions to explore the extent and the underlying mechanism of IP influencing BNF using acetylene reduction assay and <sup>15</sup>N labeling DNA-based stable isotope probing (DNA-SIP) combined with metagenomics. IP on rice root surface exhibited a diurnal Fe(III)/Fe(II) redox rhythm. In the presence of IP, the <i>nifH</i> gene abundance and nitrogenase activity were significantly increased by 1.15 × 10<sup>8</sup>~1.15 × 10<sup>11</sup> copies/g·dw and 134 ~ 566 µmol C<sub>2</sub>H<sub>4</sub>/(L·h), which enhanced the <sup>15</sup>N abundance in rice shoot and root by 36.4% and 23.1% and further facilitated 2.13 and 1.87 times more biomass accumulation than that without IP. The BNF activity was significantly inhibited by dissociating IP or breaking diurnal Fe redox rhythm. DNA-SIP revealed the enrichment of diazotrophic <i>Azotobacter</i>,<i> Burkholderia</i>,<i> Phytobacter</i> and <i>Dechlormonas</i> by IP and metagenomic binning identified the presence of genes related to BNF and extracellular electron transfer in such diazotrophs, suggesting their genetic potential to mediate synergetic BNF and Fe(III) reduction.</p>

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Unveiling the crucial role of rice root iron plaque in enhancing biological nitrogen fixation via 15N-labeling DNA-SIP and metagenomics in a model study

  • 期刊论文

  • 发表日期：

    2025年7月3日

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  • Rong Jia,
  • Linpeng Yu,
  • Mengyi Wang,
  • Yulu Wu,
  • Shiqi Liu,
  • Sining Zhong,
  • Shungui Zhou

摘要

Biological nitrogen fixation (BNF) as the primarily nitrogen supply for rice growth has lately been linked to Fe(III) reduction in paddy field. Rice root iron plaque (IP) is crucial in rhizosphere elements cycling and retaining pollutants, but the synergistic interaction between rhizospheric Fe cycle and BNF remains elusive. Herein, rice seedlings with and without IP on rice root were cultured under hydroponic conditions to explore the extent and the underlying mechanism of IP influencing BNF using acetylene reduction assay and 15N labeling DNA-based stable isotope probing (DNA-SIP) combined with metagenomics. IP on rice root surface exhibited a diurnal Fe(III)/Fe(II) redox rhythm. In the presence of IP, the nifH gene abundance and nitrogenase activity were significantly increased by 1.15 × 108~1.15 × 1011 copies/g·dw and 134 ~ 566 µmol C2H4/(L·h), which enhanced the 15N abundance in rice shoot and root by 36.4% and 23.1% and further facilitated 2.13 and 1.87 times more biomass accumulation than that without IP. The BNF activity was significantly inhibited by dissociating IP or breaking diurnal Fe redox rhythm. DNA-SIP revealed the enrichment of diazotrophic Azotobacter, Burkholderia, Phytobacter and Dechlormonas by IP and metagenomic binning identified the presence of genes related to BNF and extracellular electron transfer in such diazotrophs, suggesting their genetic potential to mediate synergetic BNF and Fe(III) reduction.