Switchgrass transcription factor PvATAF2 plays positive roles in plant root-zone low-temperature tolerance

Switchgrass (Panicum virgatum L.), as a model energy crop, is a high-quality biomass resource and offers significant ecological and economic benefits. However, low root-zone temperature during the seedling stage severely limits its rapid establishment, and the molecular mechanisms regulating this process remain unclear. In this study, we identified a NAC transcription factor, PvATAF2, in the switchgrass cultivar Alamo that showed differential growth responses to root-zone temperature variation. Our results demonstrate that heterologous expression of PvATAF2 in Arabidopsis thaliana and rice (Oryza sativa) significantly enhanced the tolerance of transgenic plants to low-temperature conditions, promoting more robust root systems, accelerated shoot growth, and altered endogenous hormone levels. Mechanistic investigations revealed that PvATAF2 binds to the CAA(A/T)T motif and activates the cytokinin response regulator PvRR44, which positively regulates cold tolerance in Arabidopsis. Yeast two-hybrid, luciferase complementation imaging (LCI), and bimolecular fluorescence complementation (BiFC) assays confirmed that PvATAF2 interacts with PvRR41 and PvARF24-3 K, respectively. Furthermore, yeast one-hybrid and dual-luciferase reporter assays indicated that PvbHLH94-1 K and PvLBD37-9 K positively and negatively regulate PvATAF2 transcription, respectively. In summary, this study elucidates the positive regulatory role of the ATAF2 gene in root-zone low-temperature tolerance in both dicot and monocot plants, an effect likely mediated through the modulation of endogenous cytokinin signaling pathways. These findings provide a theoretical foundation for the role of the NAC family in enhancing plant adaptation to root-zone low-temperature stress by regulating cytokinin B-type ARRs.