Polyamine metabolism genes of maize (Zea mays) downregulated during compatible interaction with Meloidogyne arenaria

Meloidogyne arenaria is one of the most economically important root-knot nematode (RKN) species with a wide host range, including maize. Although analyses of host-nematode interactions have highlighted the involvement of polyamines (PAs) in plant defense, the roles of spermine and spermidine synthases, crucial enzymes in PAs' biosynthesis, and polyamine oxidase, which is involved in PAs' catabolism, have not yet been investigated in the maize-RKN pathosystem. Thus, this study aimed to analyze the expression levels of genes encoding these enzymes during the compatible interactions between M. arenaria and maize (Zea mays L.).

Time course analysis was performed on maize root samples collected at three time points. Total RNA was extracted from roots and used as a template for cDNA synthesis. The relative expression level of spermine and spermidine synthases and polyamine oxidase encoding genes was analyzed using a real-time PCR assay and normalized to the reference genes (Leunig and FPGS). In the case of the spermine synthase coding gene, significant upregulation was first observed, followed by downregulation. On the other hand, in the spermidine synthase coding gene, significant downregulation in all analyzed time points was reported. Significant downregulation was also observed at 8 dpi in the polyamine oxidase coding gene.

The obtained results suggest that the downregulation of genes encoding proteins involved in PAs' biosynthesis and catabolism may partially contribute to the nematode-induced suppression of some host defense response mechanisms, which in turn may be involved in facilitating RKN colonization of the susceptible host.