SCN Basics
SCN Life Cycle
SCN Life cycle pictures (May require substantial loading time)

SCN Invasion (pictures! May require substantial loading time)
2 day
4 day
6 day
8 day

SCN databases
SCN gene database
SCN genes of interest
Soybean cv SCN race

Soybean Defense Response
Defense Response overview 
Thru the microscope
Thru microarrays
microarray database
Soybean gene database

Hypersensitive response
Oxidative burst
Systemic Acquired Resistance

R genes
R gene overview
Rhg mapping
Rhg1
Rhg4

Pathways
Jasmonic acid
Salicylic acid
Secondary products
Ethylene
Sucrose & Trehalose

Genes/enzymes              peroxidase  
copper amine oxidase

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Overview

Plants have evolved complex mechanisms to resist attack by viruses, bacteria, fungi, nematodes, insects, and other pests and pathogens. As plants evolved these resistance mechanisms, the pests and pathogens have evolved in an attempt to overcome plant resistance.  New virulent strains of bacteria and fungi constantly place selection pressure on plants in a never ending battle. In classical plant-pest interactions, the pathogen interacts with the plant, which is either resistant or susceptible to attack.  If the plant is susceptible, then the reaction between the pet and plant is a compatible interaction and the pathogen is successful in its attack.  If the plant is resistant then the resistance reaction of the plant is activated by a race-specific elicitor of the pathogen.  The elicitor is detected by a plant receptor which triggers other genes which help to defeat the pathogen.   

The most frequently occurring defense response of the plant is the hypersensitive response (HR), which occurs early during the infection process.  The HR involves the death of a few cells in the local region of pathogen attack to form a necrotic lesion that may contain antimicrobial compounds. Also, deposition of lignin and callose are triggered, as are hydroxyproline-rich glycoproteins and pathogenesis related proteins, including 1,3-B-glucanases and chitinases. Other biochemical changes include the generation of reactive oxygen species (the oxygen burst) and the production of phenolics.

Several defense related pathways may be triggered those required for the synthesis of jasmonic acid and related compounds and salicylic acid.  These compounds act as triggers for the production of other defense-related pathways and chemicals.