The Transcription Factor OsSPL9 Endows Rice with Copper Deficiency Resilience

Copper (Cu) is a crucial micronutrient essential for the growth and development of plants. Rice exhibits remarkable resistance to Cu deficiency, but the underlying molecular mechanisms are not well understood. In this study, we reveal that the plant's ability to withstand Cu deficiency is orchestrated by a transcription factor known as OsSPL9. We have demonstrated that OsSPL9 functions as a central regulator of Cu homeostasis. Disrupting OsSPL9 through knockout significantly reduces the plant's tolerance to Cu deficiency. As a result, the spl9 mutants exhibit reduced Cu accumulation in their shoots when compared to wild-type plants. This reduction is linked to a disruption in the transport of Cu from older leaves to younger ones. Furthermore, we show that OsSPL9 directly binds to GTAC motifs in the promoters of key genes involved in Cu uptake and transport, as well as Cu-miRNAs, and enhances their transcription under Cu-deficient conditions. Overall, our findings shed light on the molecular basis of rice resilience to Cu deficiency stress and place the transcription factor OsSPL9 as a master regulator of this response.