Hypersensitive response
and reactive oxygen species
In classical plant-pest interactions the
hypersensitive response (HR) occurs very rapidly. Therefore, in
this sense, the interaction of SCN with soybean does not adhere to a
classical HR, however I suspect there is an HR-like response.
There is cell death and necrosis around the SCN feeding site in SCN-resistant
soybean roots at about four days after invasion. Enzymes involved
in the generation of reactive oxygen species (ROS), such as copper amine
oxidase and peroxidase are elevated upon invasion.
Jasmonic acid pathway
We have an indication that phospholipase and
lipoxygenase are elevated in response to SCN invasion, suggesting that
jasmonic acid and derivatives are synthesized. Thus, we suspect
that downstream
products induced by JA are elevated. Certainly,
gene transcripts for enzyme involved in phenylpropanoid metabolism are
elevated.
Phenylpropanoid pathway
Transcripts of numerous genes encoding enzymes in
phenylpropanoid synthesis are elevated, including cinnamate hydrolase,
4-coumarate coA ligase, chalcone synthase, and isoflavone reductase.
Carbohydrate
The nematode is acting as a nutrient sink, drawing
off carbohydrates from the plant. Numerous transcripts are elevated for
genes encoding enzymes involved in carbohydrate metabolism.
Metabolic profiles confirm this observation.
Protein synthesis and
turnover
Observations through the microscope and biochemical
studies indicate an increase in metabolism in the syncytium.
Transcript profiles analysis indicate an increase in transcripts of
genes for rRNA proteins, ubiquitin, transcription factors, and other
genes involved in transcription, translation, and protein turnover.
Transcripts of some genes involved in the cell cycle are also elevated.
Other plant defense
responses
Transcripts of numerous other genes related to the
defense response, including proteases, are induced during SCN invasion.
Signaling
Transcripts for numerous protein kinases and GTP-binding
proteins are elevated.
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