| Summary: | 4,8-dihydroxy-l-tetralone (4,8-DHT) is an allelochemical isolated from the outer bark of <i>Carya cathayensis</i> that acts as a plant growth inhibitor. In order to explore the mechanism of 4,8-DHT inhibiting weed activity, we treated three species of <i>Digitaria sanguinalis</i>, <i>Arabidopsis thaliana,</i> and <i>Poa annua</i> with different concentrations of 4,8-DHT and performed phenotype observation and transcriptome sequencing. The results showed that with an increase in 4,8-DHT concentration, the degree of plant damage gradually deepened. Under the same concentration of 4,8-DHT, the damage degree of leaves and roots of <i>Digitaria sanguinalis</i> was the greatest, followed by <i>Arabidopsis thaliana</i>, while <i>Poa annua</i> had the least damage, and the leaves turned slightly yellow. Transcriptome data showed that 24536, 9913, and 1662 differentially expressed genes (DEGs) were identified in <i>Digitaria sanguinalis</i>, <i>Arabidopsis thaliana,</i> and <i>Poa annua</i>, respectively. These DEGs were significantly enriched in photosynthesis, carbon fixation, glutathione metabolism, phenylpropanoid biosynthesis, and oxidative phosphorylation pathways. In addition, DEGs were also enriched in plant hormone signal transduction and the MAPK signal pathway in <i>Arabidopsis thaliana</i>. Further analysis showed that after 4,8-DHT treatment, the transcript levels of photosynthesis PSI- and PSII-related genes, LHCA/B-related genes, Rubisco, and PEPC were significantly decreased in <i>Digitaria sanguinalis</i> and <i>Arabidopsis thaliana</i>. At the same time, the transcription levels of genes related to glutathione metabolism and the phenylpropanoid biosynthesis pathway in <i>Digitaria sanguinalis</i> were also significantly decreased. However, the expression of these genes was upregulated in <i>Arabidopsis thaliana</i> and <i>Poa annua</i>. These indicated that 4,8-DHT affected the growth of the three plants through different physiological pathways, and then played a role in inhibiting plant growth. Simultaneously, the extent to which plants were affected depended on the tested plants and the content of 4,8-DHT. The identification of weed genes that respond to 4,8-DHT has helped us to further understand the inhibition of plant growth by allelochemicals and has provided a scientific basis for the development of allelochemicals as herbicides.
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