SCN9A and infection: Mutants defective for either of the common symbiosis genes SYMRK, CASTOR, POLLUX, NENA, NUP85, or NUP133 produce very similar phenotypes in symbiosis, in that they abort infection at the epidermis and are impaired in calcium-spiking (Kistner et al., 2005; Miwa et al., 2006; Groth et al., 2010), which placed them at the same hierarchical level.