BTB protein MdBT2 negatively regulates iron homeostasis by interacting with MdNAC1 in apple

Abstract

NAC transcription factors play an important role in plant abiotic stress response. However, the molecular mechanism of how it regulates iron accumulation remain largely unknown in apple. Here, we show that MdNAC1 positively regulates iron accumulation under iron deficiency conditions. Overexpression of MdNAC1 show higher levels of iron accumulation and chlorophyll content as well as activated the activity of plasma membrane (PM) H + -ATPases in response to iron deficiency. Quantitative PCR (qPCR) analysis showed that the expression of several iron-related genes were significantly up-regulated in transgenic apple calli. Additionally, we identify an MdBT2 protein that interacts with the MdNAC1 protein. MdBT2 negatively regulates the protein stability of MdNAC1 by degrading it through the ubiquitinated 26S proteasome pathway. In addition, overexpression of MdBT2 in apple and Arabidopsis exhibited inhibition of iron accumulation and showed chlorosis in the new leaves. In sum, our study provided molecular and genetic evidence that the MdBT2 may negatively regulate iron response by mediating the MdNAC1 stability. • We identified an NAC transcription factor, MdNAC1, from apple and demonstrated that it was localized in the nucleus. • The over expression of MdNAC1 increased iron accumulation in transgenic apple calli and Arabidopsis. • MdBT2 interacts with MdNAC1and mediates the ubiquitination of MdNAC1.