The globodera rostochiensis Gr29D09 effector with a role in defense suppression targets potato hexokinase 1 protein

Authors: CHEN, SHIYAN - Cornell University; TRAN, TIEN THI THUY - Cornell University; YEH, ATHENA YI-CHUN - Cornell University; Yang, Huijun; CHEN, JIANSONG - Cornell University; Yang, Yong; Wang, Xiaohong

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2023
Publication Date: 1/29/2024
Citation: Chen, S., Tran, T., Yeh, A., Yang, H., Chen, J., Yang, Y., Wang, X. 2024. The globodera rostochiensis Gr29D09 effector with a role in defense suppression targets potato hexokinase 1 protein. Molecular Plant-Microbe Interactions. 37:1, 25-35. https://doi.org/10.1094/MPMI-07-23-0095-R.
DOI: https://doi.org/10.1094/MPMI-07-23-0095-R

Interpretive Summary: The golden potato cyst nematode (aka golden nematode) (Globodera rostochiensis) is an agriculturally important pest of several Solanaceous crops including potatoes. Golden nematode secretes effector proteins into root tissue to cause disease. However, knowledge on the function of nematode effectors remains limited. In this study, we have cloned four effector genes belonging to the Gr29D09 effector family, from the golden nematode. Our sequence analysis revealed that these effector genes belong to a subgroup of a highly expanded effector gene family called the Gr4D06 family. We further conducted a series of experiments to investigate the role of Gr29D09 effectors in nematode parasitism. We showed that Gr29D09 effectors act as a suppressor of plant defenses. We further showed that Gr29D09 effectors specifically interact with potato hexokinase 1 protein (StHXK1) in plant cells. Interestingly, we found that like HXK1 in the model plant Arabidopsis, StHXK1 acts as a positive regulator of plant defense. Altogether, our results suggest that targeting StHXK1 by Gr29D09 effectors may interfere with the function of StHXK1 in plant defense, thereby helping promote nematode disease. This study has increased our understanding of how nematode effectors function in host plant cells to facilitate successful infection. This information might lead to the development of novel methods for controlling golden nematode.

Technical Abstract: The potato cyst nematode (Globodera rostochiensis) is an obligate root pathogen of potatoes. G. rostochiensis encodes several highly expanded effector gene families including the Gr4D06 family; however, little is known about the function of this effector family. We cloned from G. rostochiensis four 29D09 genes (named Gr29D09v1/v2/v3/v4) that show high sequence similarity and are homologous to the Hg29D09 and Hg4D06 effector genes from the soybean cyst nematode. Phylogenetic analysis revealed that these Gr29D09 genes belong to a subgroup of the Gr4D06 family. We showed that Gr29D09 genes are expressed exclusively within the nematode’s dorsal gland cell and are dramatically up regulated in parasitic stages, indicating involvement of Gr29D09 effectors in nematode parasitism. Transgenic potato lines overexpressing Gr29D09 variants showed increased susceptibility to G. rostochiensis. Transient expression assays in Nicotiana benthamiana demonstrated that Gr29D09v3 could suppress ROS and defense gene expression induced by flg22 as well as cell-death mediated by immune receptors. These results point to a critical of Gr29D09 effectors in defense suppression. Using affinity purification coupled with nanoliquid chromatography-tandem mass spectrometry, potato hexokinase 1 (StHXK1) was identified as a candidate target of Gr29D09, which was further validated by in planta protein-protein interaction assays. Plant HXKs are involved in defense regulation against pathogen infection. We found that StHXK1 could enhance flg22-induced ROS production, consistent with a positive role of plant HXKs in defense. Altogether, our results suggest that targeting StHXK1 by Gr29D09 effectors may impair the positive function of StHXK1 in plant immunity, thereby helping promote nematode parasitism.