SPL7 Is a Master Regulatory Factor Involved in Copper Homeostasis in Arabidopsis

Abstract

Copper is an essential trance metal for all living organisms. Cu/Zn SOD (CSD1 and CSD2) are involved in scavenging of reactive oxygen species in cytosol and chloroplasts respectively and their expression is down-regulated under copper deficient conditions. Previously, we demonstrated that one of microRNA, miR398, was expressed under low-copper conditions, and degraded CSD1 and CSD2 mRNA directly. In addition, iron superoxide dismutase (FeSOD) is expressed instead of Cu/ZnSODs and complements the function under copper deficient conditions. Furthermore some of copper transporter genes are up-regulated under copper deficient conditions. Thus higher plants have strict strategy for adaptation to copper starving.
In this work, we identified a transcription factor, SPL7, involved in the activation of the miR398 transcription. Additionally, SPL7 activated the transcription of FeSOD and some of copper transporter genes. These results suggest that SPL7 is a key factor to control the adaptation mechanisms to copper deficiency.