Functional characterization of the soybean cyst nematode effector SCN-27D09 using the model plant pathogenic fungus Magnaporthe oryzae-mediated delivery system

Abstract

Soybean cyst nematode (SCN, Heterodera glycines) is widely considered as the model plant-parasitic nematode, which secretes effector proteins to manipulate host responses. In this study, we cloned a dorsal gland-expressed effector protein SCN-27D09 that belongs to the same family as Hg10A07 in SCN. We used the model plant pathogen rice blast fungus (Magnaporthe oryzae) to quickly predict and characterize the functions of SCN-27D09. By using M. oryzae secretion system in barley, we confirmed that the signal peptide of SCN-27D09 has secretory activity and can guide the protein into the host cells. Heterologous expression of SCN-27D09 in M. oryzae significantly enhanced the susceptibility of barley to M. oryzae. SCN-27D09 can inhibit Bax-triggered cell death when expressed in Nicotiana benthamiana. Overexpression of SCN-27D09 in soybean hairy root also increased the susceptibility of soybean plants to SCN. Moreover, yeast two-hybrid and firefly luciferase complementation imaging assays showed that SCN-27D09 interacts with a soybean plant kinase GmIPK-2. Functional characterization of GmIPK-2 revealed its positive role in soybean resistance, indicating that SCN-27D09 might compromise the function of GmIPK-2 to facilitate nematode infection. Our results not only uncover the biological role of SCN-27D09 in suppressing plant defense responses and therefore promoting nematode parasitism, but also reaffirm the potential application of the model plant pathogenic fungus M. oryzae in investigating the pathogenic roles of candidate effectors of phytonematodes.