# Reduced methane emissions in transgenic rice genotypes are associated with altered rhizosphere microbial hydrogen cycling

## TL;DR

Modifying rice plants to produce more PSY reduces methane emissions by changing how microbes use hydrogen in the soil around the roots.

## Contribution

This study identifies a novel strategy to reduce methane emissions from rice paddies by altering rhizosphere microbial hydrogen cycling through transgenic PSY overexpression.

## Key findings

- Transgenic rice genotypes reduced methane emissions by 38% and 58% compared to controls.
- PSY overexpression altered microbial hydrogen cycling, decreasing H2 production and increasing H2 oxidation.
- Root exudates from PSY rice contained elevated gluconeogenic acids, stimulating H2-oxidizing bacteria.

## Abstract

Rice paddies significantly contribute to atmospheric methane (CH4). Here, we show that two independent rice genotypes overexpressing genes for PLANT PEPTIDES CONTAINING SULFATED TYROSINE (PSY) reduce cumulative CH4 emissions by 38% (PSY1) and 58% (PSY2) over 70 days of growth compared with controls. Genome-resolved metatranscriptomic data from PSY rhizosphere soils reveal lower ratios of gene activities for (mostly hydrogenotrophic) CH4 production versus consumption, decreased activity of H2-producing genes, and increased activity of bacterial H2 oxidation pathways. Metabolic modeling using metagenomic and metabolomic data predicts elevated H2 oxidation and suppressed H2 production in the PSY rhizosphere. Assembled genomes of rhizosphere H2-oxidizing bacteria are enriched in genes utilizing gluconeogenic acids compared with H2-producing counterparts, and their activities are likely stimulated by elevated levels of gluconeogenic acids, primarily amino acids, in PSY root exudates. Overall, our study indicates that decreased CH4 emissions are due to a lower amount of H2 available for hydrogenotrophic methanogenesis and provides a powerful strategy to mitigate CH4 emissions from increasingly widespread rice cultivation.

Rice paddies contribute to atmospheric methane (CH4) levels. Here the authors show that increasing levels of the rice plant hormone PSY can reduce CH4 emissions by over 50% via alteration of microbial H2 cycling in the rhizosphere.