Exudation of L-canavanine from Vicia Villosa

L-canavanine, a conditionally essential nonprotein amino acid analogs to L-arginine, plays important roles in cell division, wound healing, immune function, the release of hormones, and a precursor for the synthesis of nitric oxide (NO). In this report, we found that the L-canavanine is released in relatively high amounts from the roots of hairy vetch (Vicia villosa) and declines several weeks after growth, while it was absent in bulk proxy. Hairy vetch root was able to exudate L-canavanine in both pots and in vitro conditions in an agar-based medium. The content of the L-canavanine in pots and agar conditions was higher than the field condition. It was also observed that the addition of L-canavanine significantly altered the microbial community composition and diversity in soil. Firmicutes and Actinobacteria became more abundant in the soil after the application of L-canavanine. In contrast, Proteobacteria and Acidobacteria populations were decreased by higher L-canavanine concentration (1000 nmol/g soil). Prediction of the soil metabolic pathways using PICRUSt2 estimated that the L-arginine degradation pathway was enriched by 1.3-folds when L-canavanine was added to the soil. We predicted that carbon metabolism-related pathways were altered and the degradation of nitrogen-rich compounds (i.e., amino acids) enriched. The findings of this research showed that the allelochemical L-canavanine exudates from the root of the cover crop hairy vetch, and it may be altering the soil microbial community and therefore soil metabolites pathways to increase the survival chance of seedlings. This is the first report that L-canavanine act as an allelochemical that affects the biodiversity of soil microbial community and affects the growth of succeeding plants.