Investigation of cytokinin production capacity and plant growth-promoting functions of the coral root endophytic Streptomyces spororaveus
摘要
Streptomyces spororaveus Ss06 enhanced root and shoot growth in Arabidopsis. The S. spororaveus Ss06 fermentation broth, enriched in cis-zeatin-type cytokinins, reshapes root architecture in a concentration-dependent manner and contributes to plant growth promotion. Thus, microbial cytokinins modulate plant development at the physiological level.
AbstractCytokinins are key regulators of plant growth and development, and increasing evidence indicates that plant-associated microorganisms contribute to host growth through cytokinin production. However, the physiological relevance of cis-zeatin-type cytokinins produced by Streptomyces remains largely unexplored. In this study, we investigated the plant growth-promoting effects of a coral root endophytic S. spororaveus Ss06, using Arabidopsis thaliana as a model plant. Plate co-cultivation and pot experiments demonstrated that the S. spororaveus Ss06 fermentation broth significantly enhanced primary root elongation, lateral root formation, root hair development, leaf expansion, and biomass accumulation in a concentration-dependent manner. Targeted LC–MS/MS analysis revealed a pronounced enrichment of cis-zeatin-type cytokinins, particularly 2-methylthio-cis-zeatin riboside (2MeScZR), in the fermentation broth. Bioassays using cytokinin-related Arabidopsis mutants showed that both the S. spororaveus Ss06 fermentation broth and exogenous cis-zeatin riboside promoted plant growth, with root system architecture being particularly responsive. These results provide physiological and biochemical evidence that Streptomyces-derived cis-zeatin-type cytokinins contribute substantially to plant growth promotion. This study highlights the functional relevance of microbial cytokinins in modulating plant development and advances current understanding of Streptomyces–plant interactions from a plant physiological perspective.