The ZmFKF1b-ZmDi19-5 Regulatory Module Coordinates Drought Tolerance and Flowering Time in Maize

Drought is a major environmental stress that inhibits plant growth and reduces crop yields. The Di19 gene family is known to play a pivotal role in mediating plant responses to drought. However, the mechanisms by which Di19 proteins integrate drought response with developmental processes, particularly flowering time, remain largely unknown in maize. In this study, we reveal that ZmDi19-5 possesses a dual function in regulating both drought tolerance and flowering in maize. Overexpression of ZmDi19-5 not only enhanced drought tolerance but also delayed flowering time. Furthermore, we demonstrate that the ZmDi19-5 and ZmFKF1b proteins interact both in vivo and in vitro. In contrast to the zmfkf1b mutants, plants overexpressing ZmFKF1b exhibited increased sensitivity to drought and accelerated flowering. Mechanistically, the interaction with ZmFKF1b attenuates the binding of ZmDi19-5 to the promoter of its downstream targets, including the transcription factor ZmHsf08 and the flowering inhibitor ZmCOL3, subsequently affecting their expression. In conclusion, our findings reveal that the ZmFKF1b-ZmDi19-5 module coordinates drought stress responses and flowering time in maize, providing a promising target for breeding drought-resistant maize varieties with stable agronomic traits.