Analysis of ribonuclease and peroxidase activities during maize ( Zea mays) response to Meloidogyne arenaria infection

Meloidogyne arenaria belongs to root-knot nematodes (RKNs) which constitute a group of highly polyphagous nematodes causing serious damages to many crop varieties. Maize ( Zea mays ) is one of its main hosts. During plant response to RKN infection, many mechanisms are involved. Pathogenesis-related proteins (PRs), which present many functions and enzymatic activities, such as ribonucleases (RNases), antioxidative enzymes, or proteases are involved in these processes. The aim of this study was to describe changes in peroxidase and RNase activities induced in Z. mays during its response to M. arenaria infection. Moreover, proteins potentially responsible for peroxidase activity were indicated. RNase and peroxidase activities were tested on proteins extracted from roots of healthy plants, M. arenaria infected plants, and healthy plants mixed with M. arenaria juveniles, in native polyacrylamide (PAA) gels. Samples were collected from two varieties of maize at four time points. A selected fraction showing peroxidase activity was excised from the gel and analyzed using mass spectrometry (MS) to determine protein factors responsible for enzymatic activity. As a result, the analyzed varieties showed slight differences in their RNase and peroxidase activities. Higher activity was observed in the Tasty Sweet variety than in the Waza variety. There were no significant differences between healthy and infected plants in RNase activities at all time points. This was in contrast to peroxidase activity, which was the highest in M. arenaria -infected plants 15 days after inoculation. On the basis of protein identification in excised gel fractions using MS it can be assumed that mainly peroxidase 12 is responsible for the observed peroxidase activity. Moreover, peroxidase activity may be presented by glutathione-S-transferase as well.