Summary: Autophagy, an intracellular degradation system conserved in eukaryotes, has been increasingly recognized as a key battlefield in plant–pathogen interactions. However, the role of plant autophagy in nematode parasitism is mostly unknown. We report here the identification of a novel and conserved effector, Nematode Manipulator of Autophagy System 1 (NMAS1), from plant‐parasitic cyst nematodes (Heterodera and Globodera spp.). We used molecular and genetic analyses to demonstrate that NMAS1 is required for nematode parasitism. The NMAS1 effectors are potent suppressors of reactive oxygen species (ROS) induced by flg22 and cell death mediated by immune receptors in Nicotiana benthamiana, suggesting a key role of NMAS1 effectors in nematode virulence. Arabidopsis atg mutants defective in autophagy showed reduced susceptibility to nematode infection. The NMAS1 effectors contain predicted AuTophaGy‐related protein 8 (ATG8)‐interacting motif (AIM) sequences. In planta protein–protein interaction assays further demonstrated that NMAS1 effectors specifically interact with host plant ATG8 proteins. Interestingly, mutation in AIM2 of GrNMAS1 from the potato cyst nematode Globodera rostochiensis abolishes its interaction with potato StATG8 proteins and its activity in ROS suppression. Collectively, our results reveal for the first time that cyst nematodes employ a conserved AIM‐containing virulence effector capable of targeting a key component of host autophagy to promote disease.

High population densities of the plant-parasitic nematode Paratylenchus shenzhenensis have been observed in association with stunted anthurium in Shenzhen, Guangdong Province, China. P. shenzhenensis is now recognized as a new pathogen that causes severe damage to anthurium. Commercial fields of anthurium infected by P. shenzhenensis present a patchy distribution of plants that are usually stunted and in decline and have yellowing leaves. Roots that are heavily infected by this nematode present brown, dark-brown, or black rot, and the entire root mass is often destroyed. In this study, a method of culturing P. shenzhenensis on carrot disks was established, and the effects of temperature and time on the reproduction rate (Rr = final number of nematodes/initial number of nematodes) of this nematode were assessed. The optimum temperature for culturing P. shenzhenensis on carrot disks is 25°C and, after inoculation with 20 females and 10 males at 25°C for 10 weeks, Rr reached 3,834. At the optimum temperature, a suitable extension culture time or an increase in initial inoculum density will improve the reproductive efficiency of P. shenzhenensis. Koch’s postulates were fulfilled by inoculating P. shenzhenensis on the roots of anthurium and demonstrating the pathogenicity of the nematode. Histological analyses showed that P. shenzhenensis feed endoparasitically on the roots of anthurium; whole nematode bodies were observed in the outermost epidermal cells and root hairs, and the cell walls and middle lamellae were partially dissolved because of nematode migration and feeding.

Radopholus similis is a migratory endoparasitic nematode that is extremely harmful to host plants. Venom allergen-like proteins (VAPs) are members of the cysteine-rich secretory protein family that are widely present in plants and animals. In this study, we cloned a VAP gene from R. similis, designated as RsVAP. RsVAP contains an open reading frame of 1089 bp encoding 362 amino acids. RsVAP is specifically expressed in the esophageal gland, and the expression levels of RsVAP are significantly higher in juveniles than in other life stages of R. similis. This expression pattern of RsVAP was consistent with the biological characteristics of juveniles of R. similis, which have the ability of infection and are the main infection stages of R. similis. The pathogenicity and reproduction rate of R. similis in tomato was significantly attenuated after RsVAP was silenced. In tobacco leaves transiently expressing RsVAP, the pathogen-associated molecular pattern-triggered immunity (PTI) induced by a bacterial flagellin fragment (flg22) was inhibited, while the cell death induced by two sets of immune elicitors (BAX and Gpa2/RBP-1) was repressed. The RsVAP-interacting, ras-related protein RABA1d (LeRabA1d) was identified in tomato hosts by yeast two-hybrid and co-immunoprecipitation assays. RsVAP may interact with LeRabA1d to affect the host defense response, which in turn facilitates nematode infection. This study provides the first evidence for the inhibition of plant defense response by a VAP from migratory plant-parasitic nematodes, and, for the first time, the target protein of R. similis in its host was identified.

Unlike sedentary plant-parasitic nematodes, migratory plant endoparasitic nematodes (MPENs) are unable to establish permanent feeding sites, and all developmental stages (except eggs) can invade and feed on plant tissues and can be easily overlooked because of the unspecific symptoms. They cause numerous economic losses in agriculture, forestry, and horticulture. In order to understand the pathogenetic mechanism of MPENs, here we describe research on functions and host targets focused on currently identified effectors from six MPENs, namely Radopholus similis, Pratylenchus spp., Ditylenchus destructor, Bursaphelenchus xylophilus, Aphelenchoides besseyi, and Hirschmanniella oryzae. This information will provide valuable insights into understanding MPEN effectors and for future fostering advancements in plant protection.

Helicotylenchus comprises a significant group of plant-parasitic nematodes that primarily feed on plant roots. This study focuses on the description of a newly discovered species, Helicotylenchus zenchengensis n. sp., from China. The distinguishing characteristic of this species, as observed under a microscope, is the absence of head annulation. The stylet, measuring between 23.8 and 29.3 μm, exhibits anteriorly flattened or indented stylet knobs. The elongated tail has a c value ranging from 15.8 to 22.6 and a c’ value between 1.9 and 2.4. It bears 15 to 18 tail annuli, presenting a conical shape with projections. The phasmids are located at the 4th to 10th body annulations posterior to the anus, while no males were observed. Three phylogenetic trees were constructed to determine the evolutionary relationships using the 18S rRNA, ITS, and 28S D2-D3 expansion segments of the newly discovered species and related Helicotylenchus sequences obtained from the database. Based on the ITS sequences, a phylogenetic tree revealed that H. zenchengensis n. sp. clustered with H. cuspicaudatus. However, it was distinguished from H. cuspicaudatus when examining the 18S and 28S rRNA sequences and morphological characteristics. Additionally, comprehensive and diagnostic tables for all known species of Helicotylenchus in China are provided for reference.