Transcriptomics and OsWAK24–MPK3 crosstalk reveal resistance mechanism of primed rice seedlings against arsenic–iron

Priming, elucidated as "memory," refers to the preconditioning of plant's stress responses to enhance resilience toward future stressors, including arsenic (As) contamination. This adaptive preparedness becomes further complex under As-Fe(iron) interplay, which remains scarcely delineated within priming background. Here, we employed Illumina sequencing to acquire global transcriptome alterations and heterologous interaction approach to chart the molecular reprogramming associated with As and As-Fe-dynamics in primed rice. The transcriptome revealed 3005 and 3650 genes to be differentially regulated in As and As-Fe-exposed primed seedlings. Comprehensive elucidation of expression profiling revealed that key genes were involved in transportation (OsNramp, OsFCR, OsNAS), signalling (OsWRKY, OsMYB, OsAP2, OsZF-TF), and defence (OsHSP, OsPRX, OsCyt P450). The antioxidant (OsGST, OsAPX) expression correlated well with their respective physiological enzyme activity. The entire WAK module, transducing extracellular signals to intercellular pathways, was differentially regulated under As and As-Fe influence. Notably, OsWAK24 revealed higher expression under As-Fe, reflecting its association with seedlings' tolerance behaviour. The computational protein network and docking unfolded OsMPK3 as an interactor of OsWAK24. The split-ubiquitin-based yeast-hybrid assay and immunoblot revealed OsWAK24-OsMPK3 association, suggesting OsMPK3 phosphorylates OsWAK24 at serine residue. Overall, the results decoded the seedling's resilience mechanism and aid in developing rice varieties with desired traits.