Nematode Resistance in Soybean - Translational Genomics for Crop Breeding: Biotic Stress - page 110

IAA IAA

19C07
CLE
Annexin
10A06
Cell wall degrading enzyme
Chorismate mutase
SPRYSEC19
Nuclear-targeted effectors
Cellulose-binding protein
16D10
Ubiquitin
Auxin transport
Auxin block

PIN1

PIN1

PME3
?

Cleavage

LAX3
19C07

AUX1

cell surface
(secreted)

16D10

SCR-like

alternative
secretory
pathway

CBP

CLE
peptides

?

nuclear
targeting

?

Protein
Degradation

Transcriptional
Reprogramming

PIN3

CLV2/CRN

Developmental
Reprogramming

LAX3

Feeding
tube

Chrorismate
mutase

PIN3

Chrorismate

LAX3

Metabolic
Reprogramming

Annexin

Vacuole

LAX3

Gland
ampulla

Oxidoreductase

10A06

PIN3

PIN3

SPRYSEC19

Stress & Defense
Response

SPDS2

CWDEs

CC-NB-LRR

Current Opinion in plant Biology

Fig. 7.3. Molecular mechanism of nematode effector protein action in host plant cells (adapted from Gheysen and Mitchum
2011). For a color version of this figure, please refer to the color plate.

origin were involved in this process is still
unclear (Dropkin 1963; Jones 1981). The first
characterized effectors are secreted from a cyst
nematode esophageal encode EGases (Smant
et al. 1998). EGases degrade polysaccharides
possessing

expressed in later parasitic stages, during which
syncytium continues to expand along the vascu-
lature, suggesting cell wall-degrading enzymes
of plant origin play a role in that process. Based
on the study of five tobacco EGases that are
upregulated upon infection by both root-knot and
cyst nematodes, Goellner et al. (2000) proved
that cell wall modification within plant-parasitic-
nematode feeding cells arises from cell-wall-
modifying enzymes of plant, rather than being of
nematode origin (Goellner et al. 2000). Pectate
lyase and polygalacturonase, two other cell-wall-
degrading enzymes, have also been identified
from RKN (Doyle and Lambert 2002; Jaubert
et al. 2002; Popeijus et al. 2000). They likely
play a role in nematode movement by soften-
ing the cell wall. An expansin gene was cloned
from the plant-parasitic roundworm species Glo-
bodera rostochiensis (Qin et al. 2004). Expansin
proteins have so far been identified only in plants,

-1, 4-glucan backbones, such as
cellulose and xyloglucan. In their study, the
authors isolated EGase that was synthesized in
the esophageal glands of the cyst nematodes Glo-
bodera rostochiensis and Heterodera glycines
(Smant et al. 1998). The homologous genes were
also identified in RKN and in other cyst nema-
tode species (Dautova et al. 2001; De Meut-
ter et al. 2001). EGase of nematode origin was
shown to be expressed primarily in J2 stage
and again in adult males that migrate out of the
root, supporting a role for it in cell wall degra-
dation during the penetration and intracellular
migration of the nematode through root tissue
(Goellner et al. 2000). Nematode EGases are not

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