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<p>Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) is encoded by a multigene family in rice (<i>Oryza sativa</i> L.), and its transcriptional abundance is tightly coupled with allelopathic potential. Rice chromosome 2 harbors a tandemly duplicated cluster of four <i>OsPAL</i> paralogs: <i>OsPAL2;1</i>, <i>OsPAL2;2</i>, <i>OsPAL2;3</i>, and <i>OsPAL2;4</i>. To dissect their precise roles in regulating allelopathy, this study generated independent overexpression lines for each <i>OsPAL</i> gene in both the allelopathic rice genotype ‘PI312777’ and the non-allelopathic cultivar ‘Lemont’. Overexpression of individual <i>OsPAL</i> genes significantly enhanced the inhibitory effects of root exudates on barnyardgrass growth, with <i>OsPAL2;1</i> and <i>OsPAL2;3</i> exhibiting the most pronounced weed-suppressive phenotypes. Mechanistically, <i>OsPAL</i> overexpression drove distinct tissue-specific metabolic alterations: in transgenic ‘PI312777’, concentrations of protocatechuic acid, <i>p</i>-coumaric acid, ferulic acid, salicylic acid, and cinnamic acid significantly accumulated in both roots and leaves; conversely, ‘Lemont’ overexpression lines displayed selective increases in protocatechuic acid, <i>p</i>-hydroxybenzoic acid, and cinnamic acid. Beyond direct allelochemical mediation, <i>OsPAL</i> overexpression reshaped the rhizosphere microbiome. Transgenic ‘PI312777’ lines displayed reduced alpha diversity and species richness within the root-associated bacterial community. Most strikingly, <i>OsPAL2;1</i> and <i>OsPAL2;3</i> overexpression lines showed a marked enrichment of <i>Flavisolibacter</i>, <i>Ohtaekwangia</i>, <i>Lysobacter</i>, and <i>Myxococcota</i>. Collectively, our findings demonstrate that <i>OsPAL2;1</i> and <i>OsPAL2;3</i> emerge as prime candidates for engineering next-generation rice varieties with enhanced natural weed-suppressive capacity through integrated metabolic and microbiome engineering.</p>

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OsPAL2;1 and OsPAL2;3 are Key Regulators of Phenolic Acid to Modulate Allelopathy and Rhizosphere Microbiome in Rice

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月18日

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  • Yujie Gao,
  • Enze Wu,
  • Yiqing Zhang,
  • Xinxin Peng,
  • Jianhe Li,
  • Huabin Zhang,
  • Xue Yan,
  • Jiayu Li,
  • Changxun Fang

摘要

Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) is encoded by a multigene family in rice (Oryza sativa L.), and its transcriptional abundance is tightly coupled with allelopathic potential. Rice chromosome 2 harbors a tandemly duplicated cluster of four OsPAL paralogs: OsPAL2;1, OsPAL2;2, OsPAL2;3, and OsPAL2;4. To dissect their precise roles in regulating allelopathy, this study generated independent overexpression lines for each OsPAL gene in both the allelopathic rice genotype ‘PI312777’ and the non-allelopathic cultivar ‘Lemont’. Overexpression of individual OsPAL genes significantly enhanced the inhibitory effects of root exudates on barnyardgrass growth, with OsPAL2;1 and OsPAL2;3 exhibiting the most pronounced weed-suppressive phenotypes. Mechanistically, OsPAL overexpression drove distinct tissue-specific metabolic alterations: in transgenic ‘PI312777’, concentrations of protocatechuic acid, p-coumaric acid, ferulic acid, salicylic acid, and cinnamic acid significantly accumulated in both roots and leaves; conversely, ‘Lemont’ overexpression lines displayed selective increases in protocatechuic acid, p-hydroxybenzoic acid, and cinnamic acid. Beyond direct allelochemical mediation, OsPAL overexpression reshaped the rhizosphere microbiome. Transgenic ‘PI312777’ lines displayed reduced alpha diversity and species richness within the root-associated bacterial community. Most strikingly, OsPAL2;1 and OsPAL2;3 overexpression lines showed a marked enrichment of Flavisolibacter, Ohtaekwangia, Lysobacter, and Myxococcota. Collectively, our findings demonstrate that OsPAL2;1 and OsPAL2;3 emerge as prime candidates for engineering next-generation rice varieties with enhanced natural weed-suppressive capacity through integrated metabolic and microbiome engineering.