MjCRSP, a small cysteine-rich effector protein from Meloidogyne javanica suppresses plant immunity

Meloidogyne javanica is one of the most important root-knot nematode (RKN) species causing considerable economic losses globally. Effectors which are secreted nematode molecules play an important role in mediating nematode interaction with their hosts. Specifically, small cysteine rich (SCR)- secreted proteins found across many taxa, such as bacteria oomycete and fungi are of interest for this particular study. Towards this end, we identified over 600 SCR in the genome of M. javanica, with a size range between 100 and 300 amino acids (aa) with 4 - 8 cysteine residues. We selected one of these proteins, which we named MjCRSP for further characterisation. MjCRSP was predicted to have a signal peptide at the N-terminus end and a putative nuclear localization signal (NLS) in the C-terminus region. Using Agrobacterium-mediated transient expression system in Nicotiana benthamiana, we show that this protein inhibits elicitin infestin1 (INF1)-triggered cell death and immune responses triggered by Flg22 peptide. Furthermore, subcellular localization showed that MjCRSP localizes in the cytoplasm. This study demonstrated that MjCRSP is M. javanica effector protein that modulates plant immune responses during RKN-host interactions.