Role of bacteria-derived flavins in plant growth promotion and phytochemical accumulation in leafy vegetables

Authors: AJEETHAN, NIVETHIKA - Dalhousie University; Yurgel, Svetlana; ABBEY, LORD - Dalhousie University

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2023
Publication Date: 8/28/2023
Citation: Ajeethan, N., Yurgel, S., Abbey, L. 2023. Role of bacteria-derived flavins in plant growth promotion and phytochemical accumulation in leafy vegetables. International Journal of Molecular Sciences. 24(17). Article 13311. https://doi.org/10.3390/ijms241713311.
DOI: https://doi.org/10.3390/ijms241713311

Interpretive Summary: Sinorhizobium meliloti is a soil bacteria capable to establish symbiotic nitrogen fixing symbiosis with legumes. In addition to its ability to provide plant with atmospheric nitrogen, Sinorhizobium also improves plant growth of non-legume plants by the mechanisms that are not well understood. This bacteria producing and releases a considerable amount of flavins, compounds that are essential for plant growth and development. In this study we showed that bacteria-derived flavins improved kale and lettuce growth, nutrition quality, and yield. Therefore, the application of rhizobia with improved flavin production might provide additional benefits for plant health and sustainable production of leafy vegetables.

Technical Abstract: Sinorhizobium meliloti 1021 bacteria secretes considerable amount of flavins (FLs) and can form nitrogen-fixing symbiosis with legumes. This strain is also associated with non-legume plants, however, its role in plant growth promotion (PGP) of non-legumes is not well understood. The present study evaluated the growth and development of lettuce (Lactuca sativa) and kale (Brassica oleracea var. acephala) plants inoculated with S. meliloti 1021 (FL+) and its mutant 1021'ribBA with limited ability to secrete FLs (FL-). The results from this study indicated that inoculation with 1021 significantly increased length and surface area of roots and hypocotyls of seedlings compared to the 1021'ribBA. Kale and lettuce seedlings recorded 19% and 14% increase in total root length, respectively, following inoculation with 1021 compared to 1021'ribBA. A greenhouse trial showed that plant growth, photosynthetic rate and yield were improved by 1021 inoculation. Moreover, chlorophylls a and b, and total carotenoids were increased in the plants associated with 1021. In kale, total phenolics and flavonoids were significantly increased by 6% and 23% respectively, and in lettuce these componds were increased by 102% and 57% respectively, with 1021 inoculation. Overall, the bacteria derived FLs enhanced kale and lettuce plant growth, physiology, and yield. Future investigation will use proteomic approaches combined with plant physiological responses to better understand host-plant response to bacteria-derived FLs.