Rev. 07/03/24



         Heteroderidae Filip'ev & Schuurmans Stekhoven, 1941

      Meloidogynidae (Skarbilovich, 1959)
      Meloidoderidae (Golden, 1971)
      Ataloderidae (Wouts, 1973)

Nematode genera in the family Heteroderidae can be divided into two major groups: the cyst nematodes in which the famale body becomes a hard-walled cyst, and the cystoid nematodes in which the body wall of the female does not harden (Subbotin et al., 2017).
Cyst Nematodes Cystoid Nematodes
Afenestrata (=Heterodera) Atalodera
Betulodera Bellodera
Cactodera Camelodera
Globodera Cryphodera
Heterodera Ekphymatodera
Punctodera Hylonema
Vittatidera Meloidodera
  Thecavermiculatus (=Atalodera)

Morphology and Anatomy:



Second stage juveniles:

Two sub-families:

Characteristic Heteroderinae Meloidogyninae
Feeding site Multinucleate syncytium Multinucleate giant cell
Host range Narrow Wide
Reproductive strategies Sexual Mainly parthenogenic
Eggs Mainly retained in female body Deposited in egg mass
Female body Becomes hardened cyst Does not form cyst
Hatching factors From host root exudates Favorable environmental conditions.
Root penetration Inter- and intracellular migration directly across cortex to zone of cell differentiation. Longitudinally, mainly intercellularly, toward root tip and then turning into zone of differentiating cells.

General Characteristics of cyst nematode genera

Heterodera lemon-shaped cysta, ambifenestrate, with bifenestrate vulval fenestration, or without fenestration
Globodera round cysts
Punctodera extensive fenestration
Cactodera protruding circumfenestrate vulval cone
Betulodera cyst morphology different host range




Large sectors of the developing root, including areas that would have become vascular tissue are transfomed into syncytia (Heteroderidae) or giant cells (Meloidogynidae).  Syncytia and giant cells have many plastids, mitochondria, ribosomes, increased rough endoplasmic reticulum and enlarged lobed nuclei. 

Cell wall protruberances increase the surface area of the cell membrane for flow of solutes from the xylem to the syncytium - the transfer cell configuration (Endo, 1975).

More than 50 genes are upregulated to some extent in the development of giant cells (Meloidogyne) and syncytia (Heterodera/Globodera) (Gheysen and Fenoll, 2002). Both types of feeding cells have the genome amplified as a result of multiple shortened cell cycles; but the processes differ. Giant-cells go through repeated (acytokinetic) mitosis.  Syncytia undergo repeated S-phase endoreduplication without mitosis or nuclear division. 

The eukaryotic cell cycle has four stages.:
1. Nuclear DNA is replicated during synthesis phase (S-phase).
2. DNA synthesis is followed by an interval called the G2 phase (G=gap).
3.  Mitosis occurs, the nucleus divides (M-phase).
4.  The interval between the completion of mitosis and the beginning of DNA synthesis is the G1-phase,

 In normal cell division, the cell divides (cytokinesis) after the mitosis phase.

In the root-knot nematode (Meloidogyne) feeding site there is repeated nuclear division (S and M phases of the cell cycle) but no cell division; this is called acytokinetic mitosis or karyokinesis without cytokinesis.

In the cyst nematode (Heterodera, Globodera) feeding site, the S phase of the cell cycle is activated but not the M phase.   Instead, the cells repeatedly go through the S-phase (endoreduplication) and probably through parts of the  G1 and G2 phases, but bypass mitosis.

The Cell Cycle:  modified from Gheysen and Fenell, 2002.

Since nematodes in the Heteroderidae become sedentary from the late second stage onwards (except for the metamorphosis to males), the feeding site in the plant must be maintained in a condition favorable for perhaps five or six weeks to allow the nematode to fulfill its reproductive potential.  Besides stimulation of the cell cycle events, pathogen-triggered immunity (PTI) responses, including activation of the salicylic acid pathway, must be suppressed. The salicylic acid pathway leads to production of active oxygen molecules and hypersensitive cell death.  In the Meloidogynidae, a possible candidate for effector-triggered suppression of PTI is chorismate mutase, produced in the nematode esophageal glands.  In PTI responses, chorismate is converted to salicylic acid to iniate the defense events.  Chorismate mutase from the nematode reduces chorismate, and thus salicylic acid (Smant and Jones, 2011). In Heteroderinae, the Hg30C02 effector protein of Heterodera glycines may be involved in active suppression of host defenses. The same gene occurs in H. schachtii but not in Meloidogyne spp. (Hamamouch et al., 2012).

As of 2013, some 70 proteins, many new or unknown, have been detected in nematode secretions into plant cells (Thomas Baum, pers. com.)



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