MdHMGB15-MdXERICO-MdNRP module mediates salt tolerance of apple by regulating the expression of salt stress-related genes

Abstract

Introduction

Soil salinity is an important limiting factor for plant growth. As a RING-type E3 ubiquitin ligase, MdXERICO is highly responsive to salt stress and can enhance the salt tolerance of plants. However, the molecular mechanism for the response of MdXERICO to salt stress remains unclear.

Objectives

This study aims to dissect the molecular mechanisms for MdXERICO to regulate plant response to salt stress.

Methods

Transcriptome data were compared to obtain the salt stress-induced gene MdXERICO. Transgenic apple seedlings, apple calli, Arabidopsis, and tomato material were obtained using Agrobacterium-mediated transformation assays. Semiendogenous co-immunoprecipitation analysis, yeast two-hybrid, pull-down and dual-luciferase reporter system were used to detect the protein–protein interactions. Electrophoretic mobility shift assay, yeast one-hybrids, dual luciferase and Gus staining assay were employed to verify the protein-DNA interactions.

Results

The results revealed that MdXERICO interacted with MdNRP and improved salt tolerance of apple by ubiquitinating and degrading MdNRP via the 26S proteasome pathway. Moreover, the HMG box-containing transcription factor MdHMGB15 interacted with the MdXERICO promoter, thereby activating its expression and enhancing the salt tolerance of apple.

Conclusion

This study explores the apple’s tolerance to salt stress through the MdHMGB15-MdXERICO-MdNRP module, and provides potential targets for engineering salt-tolerant varieties.