Functional SNPs in resistance gene with essential role in plant nematode defense response.

Serine hydroxymethyltransferase (SHMT) is an ubiquitous enzyme present in prokaryotes and eukaryotes, including bacteria, yeasts, plants, animals and humans. SHMT is essential for cellular one-carbon and folate metabolisms, and it is involved in pathogenesis phenomena: in humans, mutations in SHMT have been associated to a wide range of disease development, whereas in plants, specific versions of SHMT can determine resistance to phytoparasitic nematodes (PPNs).PPNs cause economically important crop losses worldwide. PPNs acquire folate from their diet at developing feeding sites in the root apparatus. Modifications of the plant's folate pathway lead to a nutritional deficiency that starves the nematode and causes the degeneration the feeding cells.In model systems such as Glycine max L. infected by PPNs, the role of SHMT in host-nematode interaction mediated is further supported by the characterization of two resistance loci, i.e. Rgh1 and Rgh4 and the identification of functional SNPs. Accessions of Solanum Lycopersicum L., and Pisum sativum L., known to be resistant to PPNs have not yet described at the SHMT loci. Therefore, we have amplified and sequenced Rgh1 in such accessions in order to explore the presence of functional SNPs described in gmRhg1. The Rgh1 sequences carry amino-acidic sequence typical of the susceptible gmRhg1, both in resistant tomato and in pea, i.e. SNP130 (R130P) and SNP358 (Y358N). We have extended this analysis to tolerant accessions of Cicer arietinum L. to PPNs and we have confirmed what it was already known in tomato and pea.However, expression analysis in roots and shoots revealed significant up-regulation of caRgh1 exclusively in PPNs-infectedplants. The analysis suggests that a different not-fully characterized mechanism of resistance exists in host-PPN interactions.