RsMYB90, a R2R3-MYB transcription factor, plays a positive role in regulating low temperature stress in radish.

The taproot of radish (Raphanus sativus L.) is vulnerable to low temperature stress. MYB transcription factors are essential in the response to low temperature stress in plants. However, little is known about how MYBs participate in the low temperature stress response in radish. A key candidate gene was significantly induced by low temperature based on transcriptome data, and its biological functions were verified using Agrobacterium-mediated genetic transformation. The target genes regulated by RsMYB90 were identified with a yeast one-hybrid (Y1H) assay and dual luciferase assay (DLA). Transgenic radish with RsMYB90 knockdown had decreased coldtolerance, while RsMYB90-overexpressing Arabidopsis showed enhanced resistance to low temperature. Additionally, the Y1H assay demonstrated that RsMYB90 could directly bind to the promoter of cold-related gene RsCOR78, and the DLA showed that RsMYB90 activated its expression. RsMYB90 promoted anthocyanin accumulation and stimulated reactive oxygen species (ROS) scavenging in response to low temperature. We propose a working model indicating how RsMYB90 functions in the low temperature stress response. The RsMYB90 gene was induced by cold conditions and directly bound to the RsCOR78 promoter, activating its expression and enhancing plant cold tolerance. RsMYB90 directly activated RsUFGT expression, promoting anthocyanin synthesis and facilitating ROS scavenging to further strengthen cold resistance. These results provide novel insights into the modulation mechanism by which MYB TFs are involved in cold tolerance in radish.