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

Priming (a form of memory) refers to the pre-conditioning of plant stress responses to enhance resilience towards future stressors, including arsenic (As) contamination. This adaptive preparedness becomes more complex under As-Fe (iron) interplay, which has not been delineated in a priming background. Here, we employed Illumina sequencing to acquire global transcriptome alterations, and a heterologous interaction approach to chart the molecular reprogramming associated with As and As-Fe dynamics in primed rice. The transcriptome revealed that 3005 and 3650 genes are differentially regulated in As- and As-Fe-exposed primed seedlings. Comprehensive expression profiling revealed that key genes were involved in transportation (OsNramp, OsFCR, and OsNAS), signalling (OsWRKY, OsMYB, OsAP2, and OsZF-TF), and defence (OsHSP, OsPRX, and OsCyt P450). Expression of antioxidant genes (OsGST and OsAPX) correlated well with their respective physiological enzyme activity. The entire wall-associated kinase (WAK) module, transducing extracellular signals to intercellular pathways, was differentially regulated under the influence of As and As-Fe. Notably, OsWAK24 revealed higher expression under As-Fe, reflecting its association with the tolerance behaviour of seedlings. The computational protein network and docking revealed OsMPK3 as an interactor of OsWAK24. Split-ubiquitin-based yeast hybrid assay and immunoblot revealed OsWAK24-OsMPK3 association, suggesting that phosphorylation mediated interaction of OsWAK24 and OsMPK3 at a serine residue. Overall, the results decoded the resilience mechanism of seedlings and will aid in developing rice varieties with desired traits.