Reduced Strigolactone Synthesis Weakens Drought Resistance in Tall Fescue via Root Development Inhibition

Drought stress significantly hampers plant growth and productivity. Strigolactones (SLs), a class of carotenoid-derived plant hormones, are recognized for their pivotal role in modulating plant morphology and enhancing drought resistance. Nonetheless, the underlying mechanisms through which SLs influence drought tolerance in tall fescue remain largely unexplored. In this study, we employed TIS108 to inhibit SL biosynthesis under drought conditions and assessed a range of morphological and physiological parameters in tall fescue, including biomass both above and below ground, antioxidase activities, proline and soluble sugar contents, and survival rates, across treatments of drought and drought coupled with TIS108 inhibition. Our findings demonstrate that the suppression of SL synthesis detrimentally affects the drought resilience of tall fescue. Through comprehensive transcriptome sequencing and subsequent qRT-PCR analyses of samples subjected to drought with and without TIS108 treatment, we identified a marked downregulation of genes involved in auxin metabolism and root development. This downregulation correlated with significant reductions in total root length, root surface area, and the number of root tips under drought stress conditions. Collectively, our research elucidates that the inhibition of SL synthesis impairs drought tolerance in tall fescue by constraining root growth and development, mediated through the modulation of auxin metabolism.