The distribution and effect of intracellular rickettsia‐ like micro‐ organisms infecting second‐ stage juveniles of the Potato cyst‐ nematode Globodera rostocbiensis

Abstract

For the first time rickettsia‐like micro‐organisms are illustrated infecting most tissues of second‐stage juveniles of Globoderu rostochiensis. They were seen only inside host cells, except for the few degenerating forms in the intestinal lumen. They were most common in the non‐contractile (sarcoplasmic) region of body wall muscles. A study of the oesophageal glands of the nematode suggested that micro‐organisms present within these glands would be unlikely to pass out of them and that the nematode would not act as a vector of these micro‐organisms to its host plants. No micro‐organisms were found in the genital primordia of the nematodes. Stored, hatched juveniles appeared to contain more microorganisms than newly hatched juveniles, indicating an increase in the intensity of the infection subsequent to hatching. No obvious signs of pathogenicity were observed in the nematodes. Uninfected juveniles apparently live longer than infected ones in viro, probably because infected juveniles exhaust their lipid reserves sooner than uninfected juveniles. The possible effect of the micro‐organisms on their nematode hosts and their potential as biological control agents are discussed.

Comparative Genomics of Wolbachia–Cardinium Dual Endosymbiosis in a Plant-Parasitic Nematode

“…This gene is located directly adjacent to the phage-like putative protein translocation system (PLTS) along with numerous ATP-/transport-related genes, suggesting possible coordination of fatty-acid metabolic activities. This result is consistent with previous experiments implicating Cardinium in nematode lipid metabolism in the juvenile infective stage ( Walsh et al, 1983b ). Recent transcriptome analysis ( Gardner et al, 2018 ) support ATP-binding and transport as important functions in this Cardinium .…”

“…For Wolbachia , PCR prevalence data showed that about half of the P. penetrans individuals analyzed were infected, indicating a non-obligate association and potentially imperfect vertical transmission in P. penetrans , contrasting with data previously reported for wRad in R. similis ( Haegeman et al, 2009 ). The tissue distribution of Cardinium in P. penetrans matched that reported from cyst nematodes G. rostochiensis, H. goettingiana, H. avenae , and H. glycines ( Shepherd et al, 1973 ; Endo, 1979 ; Walsh et al, 1983a , b ; Noel and Atibalentja, 2006 ; Yang et al, 2017 ), with presence throughout the tissues of the nematode body including the ovary walls and oocytes, although it was unclear whether cPpe occupied the esophageal glands. In contrast to wPpe, PCR showed cPpe to be at nearly 100% prevalence in this P. penetrans population, consistent with data from Heterodera spp.…”

“…In contrast to wPpe, PCR showed cPpe to be at nearly 100% prevalence in this P. penetrans population, consistent with data from Heterodera spp. ( Walsh et al, 1983a , b ). In theory, obligate mutualism could lead to 100% prevalence, but this is not known in Cardinium .…”

“…Results hinted at an intermediate role for this PPN Wolbachia (strain wPpe) between parasitic and beneficial ( Brown et al, 2016 ). TEM and light microscopy have described a Cardinium -like endosymbiont in four species of PPN, the potato cyst nematode Globodera rostochiensis ( Shepherd et al, 1973 ; Walsh et al, 1983a , b ), the cereal cyst nematode Heterodera avenae ( Yang et al, 2017 ), the pea cyst nematode Heterodera goettingiana ( Shepherd et al, 1973 ), and the soybean cyst nematode Heterodera glycines ( Endo, 1979 ; Noel and Atibalentja, 2006 ), with the present study adding a fifth record in P. penetrans ( Denver et al, 2016 ). The Cardinium strain in H. glycines was originally named Candidatus Paenicardinium endonii ( Noel and Atibalentja, 2006 ) and subsequently re-assigned to Candidatus C. hertigii ( Nakamura et al, 2009 ).…”

“…Prior to the present study, genomic and FISH analyses were unavailable. Early work suggested the H. glycines Cardinium strain might confer a benefit to its host based on occurrence at 100% prevalence, lack of pathological signs, and close association with ribosomes and host nuclei in the esophageal glands ( Shepherd et al, 1973 ; Endo, 1979 ; Walsh et al, 1983a , b ; Noel and Atibalentja, 2006 ). Occurrence in the esophageal glands has significance because of the mode of infection in PPNs by which they secrete plant cell-wall degrading enzymes from these glands to enter roots.…”