Dissecting the role of strigolactone perception in barley tolerance to cadmium or zinc stress based on the receptor mutant analysis.

Strigolactones (SLs) are plant hormones involved in development and environmental responses, but their role in heavy metal stress tolerance has not been fully characterized. We examined how SL perception affects barley (Hordeum vulgare) responses to cadmium (Cd) or zinc (Zn) toxicity by comparing wild-type (WT) plants and the SL-insensitive hvd14.d mutant. Phenotypic, ionomic, and transcriptomic analyses revealed that hvd14.d is more sensitive to both metals, exhibiting greater growth inhibition, increased Cd accumulation, altered Zn partitioning, and reduced photosynthetic performance. Elevated oxidative stress markers and weaker antioxidant responses further reflected an impaired redox balance in the mutant. Transcriptomic profiling revealed that SL signaling influences genes controlling detoxification, metal transport, and reactive oxygen species (ROS) homeostasis. Genes associated with ABA signaling were less responsive in hvd14.d, suggesting that SL perception contributes to the coordination of ABA-related pathways during metal stress. Transcription factor (TF) analyses identified distinct but overlapping groups of SL-dependent TFs under Cd and Zn exposure, including shared regulators. To date, most studies have focused on exogenous application of synthetic SLs; this work is the first to examine the role of endogenous SL perception in barley responses to heavy metal stress. Our findings demonstrate that SL perception influences both transcriptional programs and physiological processes essential for metal tolerance and redox regulation.