Early responses of susceptible and resistant soybean cultivars
as observed with the microscope
These observations are derived from the
literature. See references at the end of this page..
Endoplasmic reticulum closest to stylet is not associated with
mitochondria; surrounding cytoplasm has rough ER interspersed among
numerous mitochondria, plastids and other organelles.
In most resistant cultivars, the syncytial
cytoplasm contains extensively distributed wide cisternae, extending
throughout the rough ER. Cisternae
are less prevalent in susceptible cultivars.
Syncytia in susceptible and resistant cultivars at
18 hrs to 4 days after inoculation were hypertrophied and hyperplastic,
contained expanded regions of cell-wall dissolutions and cell-wall
depositions of callose, and sometimes included lysosome-like particles.
SCN
Susceptible Soybean
Lee at 18hr
The dense cytoplasm in the syncytium and adjacent cells surround
an enlarged vacuole. There is an abundance of ribosomes and clusters of rough
endoplasmic reticulum.
Lee at 3 Days
Cell wall dissolution is extensive and cells adjacent to syncytial cell
have large vacuoles. There is extensive proliferation of membranes and
the cell membrane near the vascular tissue is invaginated and extensive,
perhaps to allow faster passage of nutrients into the syncytium, which
is acting like an energy and nutrient sink, due to nematode
feeding. The outside cell wall of the syncytium is thickened,
presumably so the syncytium doesn't burst from increased turgor
pressure. Polyhedral-to-spherical vesicles accumulate at
termini of separated walls within syncytium
Lee Day at 4
The density of the cytoplasm is increased and there is accumulation of
endoplasmic reticulum, mitochondria, lipid droplet or secretion
granules, and plastids. Small to moderate sized vacuoles are
distributed throughout the syncytium and the cytoplasmic density is increased
in conjunction with the accumulation of ER, mitochondria, lipid droplets or secretion
granules, and plastids. There are small to moderate sized vacuoles distributed
throughout the cytoplasm and callose depositions occur on the walls of cells
adjacent to the syncytium. There are feeding tubes near feeding
site, a feeding plug site for re-entry of stylet and secretion granules.
SCN Resistant Soybean
Bedford at 18 hr
The endoplasmic reticulum increases with smooth ER near stylet and
mitochondria also increase, suggesting increased protein synthesis and
energy production. There is cell wall dissolution and a continuity of cytoplasm among
adjacent pericyclic cells, with numerous vacuoles of variable size
distributed through the cells. The cytoplasm of the syncytium is more electron-opaque than adjacent
cells and the rough ER and its large cisternae are interspersed with
numerous mitochondria.
PI88788 at 3 days
There are dense accumulations of smooth and rough ER
within the syncytium and the appearance of deteriorating cells and near necrotic cells around
syncytium. Hyperplastic, extensive cell-wall depositions are
apparent and cell walls are thickened with strand-like particulate
deposits. There are numerous sites of active Golgi.
Pickett 71 at 4 days
There is an almost empty central region of once-established
syncytium, which is almost devoid of organelles.
Refs
Endo, BY. Cellular responses
to infection. Ch. 4. in Biology and Management of the soybean
cyst nematode. (eds. R.D. Riggs and J.A. rather) APS Press, St. Paul.
1992
Endo, BY. 1991. Revue Nematol
14(1):73-94
Endo, BY. 1964. Phytopathol.
54:79-88
Endo, BY, JA Veech. 1970. Phytopathol. 60:1493-1498
Gipson, I, KS Kim, RD Riggs. 1971. Phtopathol.
61:347-353
Kim, YH, RD Riggs, KS Kim.
1987. J. Nematol. 18 (2):177-187
Mahalingam, R, HT Skorupska.
1996. Genome 39:986-998
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