Differential expression of sweetpotato nodulin 26-like intrinsic protein (NIP) genes in response to infection with the root knot nematode

Sweetpotato (Ipomoea batatas L.) is susceptible to infection by the root knot nematode (RKN) Meloidogyne incognita, which results in significant reductions in the yield of this important tuber crop worldwide. Previously, transcriptome analysis revealed differential gene expression between the roots of RKN-susceptible and -resistant sweetpotato cultivars after RKN infection, raising the possibility of identifying the genes involved in protection against RKN infection. A number of trait-specific and/or response-specific genes were also identified, including RKN infection-responsive aquaporin protein encoded by the nodulin-26-like intrinsic protein (NIP) gene. Therefore, in this study, we investigated the role of NIP genes in the defense response to RKN infection in susceptible and resistant sweetpotato cultivars. A comparison of the nucleotide sequences of sweetpotato with those of its closely related species, morning glory, revealed a group of NIP genes that could be categorized into four different ortholog groups. These four groups contained several unique genes that showed changes in expression in sweetpotato roots after RKN infection. These results indicate that NIP genes could have a potential role in protecting sweetpotato roots from RKN infection.