Pectin demethylation-mediated cell wall Na⁺ retention positively regulates salt stress tolerance in oilseed rape

Integrated phenomics, ionomics, genomics, transcriptomics, and functional analyses present novel insights into the role of pectin demethylation-mediated cell wall Na⁺ retention in positively regulating salt tolerance in oilseed rape. Genetic variations in salt stress tolerance identified in rapeseed genotypes highlight the complicated regulatory mechanisms. Westar is ubiquitously used as a transgenic receptor cultivar, while ZS11 is widely grown as a high-production and good-quality cultivar. In this study, Westar was found to outperform ZS11 under salt stress. Through cell component isolation, non-invasive micro-test, X-ray energy spectrum analysis, and ionomic profile characterization, pectin demethylation-mediated cell wall Na⁺ retention was proposed to be a major regulator responsible for differential salt tolerance between Westar and ZS11. Integrated analyses of genome-wide DNA variations, differential expression profiling, and gene co-expression networks identified BnaC9.PME47, encoding a pectin methylesterase, as a positive regulator conferring salt tolerance in rapeseed. BnaC9.PME47, located in two reported QTL regions for salt tolerance, was strongly induced by salt stress and localized on the cell wall. Natural variation of the promoter regions conferred higher expression of BnaC9.PME47 in Westar than in several salt-sensitive rapeseed genotypes. Loss of function of AtPME47 resulted in the hypersensitivity of Arabidopsis plants to salt stress. The integrated multiomics analyses revealed novel insights into pectin demethylation-mediated cell wall Na⁺ retention in regulating differential salt tolerance in allotetraploid rapeseed genotypes. Furthermore, these analyses have provided key information regarding the rapid dissection of quantitative trait genes responsible for nutrient stress tolerance in plant species with complex genomes.