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Background and aims <p>Natural grasslands are often nitrogen-limited. Even slight variations in nitrogen levels can significantly alter plants and microbial growth, and their interactions.&#xa0;While <i>Epichloë</i>&#xa0;endophytes are well-documented to promote host plant growth, it remains unclear how nitrogen availability modulates the effects of endophyte infection on host plant growth and metabolism.</p> Methods <p>In this study, we used&#xa0;endophyte-infected (E +) and endophyte-free (E-) <i>Achnatherum sibiricum</i> to investigate the effects of endophyte infection on host growth and metabolism under low (0.5&#xa0;mM N), moderate (7.5&#xa0;mM N), and high (12.5&#xa0;mM N) nitrogen conditions.</p> Results <p><i>Epichloë</i> endophytes conferred the most pronounced positive effects on host plants under moderate nitrogen conditions. Specifically, <i>Epichloë</i> upregulated genes involved in nitrogen transport and assimilation, photosynthesis, and indole-3-acetic acid (IAA) biosynthesis, leading to increased levels of total carbon, amino acids, and IAA. These changes stimulated biomass production and secondary metabolites (total phenolics and total alkaloids). Under low nitrogen, although E + plants showed upregulation of nitrogen assimilation and photosynthetic genes, this did not enhance plant growth, but did promote the accumulation of total phenolics and total alkaloids. Under high nitrogen, the promotional effect of <i>Epichloë</i> endophytes on nitrogen metabolism and photosynthesis genes was attenuated; while IAA levels remained elevated in E + plants compared to E- plants, <i>Epichloë</i> led only to an increase in total alkaloids accumulation, without promoting plant growth.</p> Conclusion <p>These findings demonstrate that <i>Epichloë</i> endophytes most strongly promote plant growth under moderate nitrogen supply, highlighting the nitrogen-dependent requirements of the grass-endophyte symbiosis.</p>

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Nitrogen supply mediated the effects of Epichloë endophytes on the growth and secondary metabolism of Achnatherum sibiricum

  • 期刊论文

  • 发表日期：

    2026年1月7日

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  • Tianzi Qin,
  • Xinjian Shi,
  • Nannan Li,
  • Yanwei Hou,
  • Zhengqin Wu,
  • Lei Chen,
  • Nianxi Zhao,
  • Yubao Gao,
  • Anzhi Ren

摘要

Background and aims

Natural grasslands are often nitrogen-limited. Even slight variations in nitrogen levels can significantly alter plants and microbial growth, and their interactions. While Epichloë endophytes are well-documented to promote host plant growth, it remains unclear how nitrogen availability modulates the effects of endophyte infection on host plant growth and metabolism.

Methods

In this study, we used endophyte-infected (E +) and endophyte-free (E-) Achnatherum sibiricum to investigate the effects of endophyte infection on host growth and metabolism under low (0.5 mM N), moderate (7.5 mM N), and high (12.5 mM N) nitrogen conditions.

Results

Epichloë endophytes conferred the most pronounced positive effects on host plants under moderate nitrogen conditions. Specifically, Epichloë upregulated genes involved in nitrogen transport and assimilation, photosynthesis, and indole-3-acetic acid (IAA) biosynthesis, leading to increased levels of total carbon, amino acids, and IAA. These changes stimulated biomass production and secondary metabolites (total phenolics and total alkaloids). Under low nitrogen, although E + plants showed upregulation of nitrogen assimilation and photosynthetic genes, this did not enhance plant growth, but did promote the accumulation of total phenolics and total alkaloids. Under high nitrogen, the promotional effect of Epichloë endophytes on nitrogen metabolism and photosynthesis genes was attenuated; while IAA levels remained elevated in E + plants compared to E- plants, Epichloë led only to an increase in total alkaloids accumulation, without promoting plant growth.

Conclusion

These findings demonstrate that Epichloë endophytes most strongly promote plant growth under moderate nitrogen supply, highlighting the nitrogen-dependent requirements of the grass-endophyte symbiosis.