Nickel phytoremediation potential of Plantago major L.: Transcriptome analysis

Plantago major L, a ubiquitous perennial weed thriving in diverse harsh environments, possesses a substantial reservoir of resistance genes, particularly those conferring resistance to heavy metals. Despite its prevalence, the intricate molecular mechanisms underpinning its exceptional ability to endure heavy metal pollution remain largely unexplored. Through transcriptome analysis, this study intended to reveal the mechanisms behind the enrichment of heavy metal Ni (nickel) in P. major and its potential for phytoremediation. In total, 7848 differentially expressed genes (DEGs) exhibited dynamic changes in tissues treated with different Ni concentrations. It was discovered that the root of P. major exhibited a more pronounced and significant response when exposed to higher concentrations of Ni. Furthermore, the upregulated genes associated with adversity stress were significantly observed in response to Ni stress. The majority of pathways related to plant growth and photosynthesis were significantly reduced; however, pathways related to metabolite synthesis, chitin synthesis, and adversity signal transduction were stimulated, and pathways related to root cell wall organization or biogenesis were suppressed. We identified that the rate-limiting enzyme PmHISN1A/B in the histidine synthesis pathway significantly enhanced Ni tolerance of the transgenic Arabidopsis without side effects, which was different to its Arabidopsis homologs. The study uncovered a molecular basis for the Ni tolerance of P. major, a heavy metal remediation plant, and provided potential genetic resources to cultivate novel P. major varieties or breed stress resilience crops.