Heterodera schachtii enolase does not elicit canonical immune responses in Arabidopsis thaliana

Enolase (2-phospho-D-glycerate hydrolase, EC 4.2.1.11) is a conserved glycolytic enzyme that catalyzes the reversible dehydration of 2-phosphoglycerate to phosphoenolpyruvate. In animal- and entomopathogenic nematodes, enolase has been shown to interact with host organisms and activate immune responses. In the plant-parasitic cyst nematode Heterodera schachtii, an established model species, enolase is hypothesized to be similarly exposed to host plant tissues during infection, based on its identification in the secretomes of related plant-parasitic nematodes. Unlike animals, plants lack an adaptive immune system and instead rely on innate immune responses to detect pathogen-derived molecules. Therefore, we investigated whether H. schachtii enolase can activate plant immune responses and influence growth and development in its host, Arabidopsis thaliana. Recombinant H. schachtii enolase was heterologously expressed in Escherichia coli and confirmed to be enzymatically active. Treatment of A. thaliana seedlings with purified enolase did not induce reactive oxygen species production, a hallmark of early plant immune activation. A concentration of 85 \(\upmu\) g/ml had no effect on plant growth; only at the highest applied concentrations (425–850 \(\upmu\) g/ml) was shoot growth reduced, while root growth remained unaffected. Consistently, quantitative PCR analysis of canonical defense marker genes (FRK1, NHL10, PAD3, CYP81F2, and JAZ10) showed no robust transcriptional activation of plant immune pathways. Together, these results indicate that H. schachtii enolase does not function as an elicitor of canonical plant immune responses.