# Overexpression of BnaMATE43b Improves Resistance to Aluminum Toxicity and Identification of Its Upstream Transcription Factors in Rapeseed (Brassica napus L.)

## TL;DR

This study shows that overexpressing the BnaMATE43b gene in rapeseed improves resistance to aluminum toxicity and identifies key transcription factors that regulate it.

## Contribution

The study identifies BnaMATE43b as a key gene for aluminum tolerance in rapeseed and discovers its upstream transcription factors.

## Key findings

- BnaMATE43b overexpression increases aluminum tolerance in rapeseed through enhanced antioxidant enzyme activities.
- Twenty-two upstream transcription factors of BnaMATE43b were identified, including four validated through interaction assays.
- Transcriptome analysis revealed enriched pathways related to stress response and metabolism in overexpression lines.

## Abstract

The multidrug and toxic compound extrusion (MATE) protein plays a crucial role in mediating plant responses to aluminum (Al) toxicity. The key candidate gene BnaMATE43b related to Al toxicity stress in rapeseed was identified using GWAS and transcriptome analysis. In this study, the BnaMATE43b gene was cloned and functionally characterized in rapeseed. Compared with wild-type rapeseed (WT), the BnaMATE43b overexpression lines (OE) demonstrated stronger aluminum tolerance, specifically manifested in higher relative elongation of taproots (RETs) and relative total root length (RTRL); under Al toxicity stress, the enzyme activities (SOD and POD) and root activity were significantly increased in the OE lines, whereas the MDA content and relative electrical conductivity were reduced in rapeseed root. Further transcriptome analysis of OE-3 showed that the differentially expressed genes (DEGs) were mainly enriched in zeatin biosynthesis (map00908), glucosinolate biosynthesis (map00966), phenylpropanoid biosynthesis (map00940), and ascorbate and aldarate metabolism (map00053). In addition, the yeast cDNA library of rapeseed was constructed, and twenty-two candidate upstream transcription factors (UTFs) of BnaMATE43b were screened; furthermore, four candidate UTFs were obtained through one-on-one interaction validation and luciferase assays, comprising three bHLH transcription factors (BnaA02g28220D, BnaA06g07840D, and BnaA08g24520D) and one ERF transcription factor (BnaA05g23130D). Collectively, these results suggest that BnaMATE43b could improve Al tolerance in rapeseed by mediating antioxidant enzyme activities and the related metabolic pathway, while the obtained UTFs lay the foundation for further analysis of the gene regulatory network under Al toxicity stress.