Integrating physiological and transcriptomic analyses reveal the role of LrDREB2B in thermotolerance of Lycoris radiata.

Heat stress (HS) has become an increasingly severe constraint on plant growth, quality and yield under global warming. However, the thermotolerance mechanisms of Lycoris radiata (L. radiata) remain underexplored. Here, we found that high temperature (42°C) induced rapid leaf wilting and rolling L. radiata leaves, accompanied by decreased chlorophyll content, reduced Fv/Fm and relative water content, and increased membrane damage and ROS accumulation. Further transcriptome analysis revealed significant enrichment the term of "response to heat", and we mainly focused on DREB-A2 transcription factor, LrDREB2B, which was upregulated by HS. LrDREB2B was localized in the nucleus and exhibited transcriptional activation activity. With the transient expression assays, overexpression of LrDREB2B enhanced the thermotolerance of L. radiata, whereas silencing LrDREB2B by virus-induced gene-silencing (VIGS) technology exhibited the opposite phenotype. Further analysis revealed that LrDREB2B overexpression increased the transcript abundance of multiple heat-responsive genes, antioxidant enzyme genes and Galactinol synthase 1 (GolS1), while silencing LrDREB2B reduced their expression. Together, our studies are the first in L. radiata to report that LrDREB2B plays a crucial role in mediating thermotolerance, providing a promising genetic target for improving heat resilience in bulb crops and other plants.