Poster: Plant Insect/Nematode Interactions

Abs # 682: Crosstalk between the different defense pathways during soybean cyst nematode and soybean interaction as determined by expression profiling

Presenter:	khan, rana , khanr@ba.ars.usda.gov
Authors	khan, rana  (A)   MacDonald, Margaret  (A)   Alkharouf, Nadim  (B)   Chouikha, Imed  (B)
Affiliations:	(A): Soybean Genomics Improvement Lab, USDA, Beltsville Maryland (B): School of computational Sciences, George Mason University, Fairfax VA

The soybean cyst nematode (SCN) is the major pest of soybean in the US and causes an estimated one billion dollars worth in damage each year. The defense response of soybean to SCN is a multigenic trait and varies depending upon the genotypes of soybean and SCN. We looked at the gene expression profile of approximately 6000 genes in nematode, salicylic acid, jasmonic acid and ethylene treated soybean plants. Preliminary results indicate that SA pathway is turned on by nematodes, but not the JA or ethylene signaling pathways. The expression of some marker genes of these different defense pathways was also determined by RT-PCR.Our results also indicate that the SA and JA signaling pathways are mutually exclusive. To test if turning on these pathways was providing any protection against the invading nematode, we induced the SA and JA- pathways by treating the plants with these chemical compounds in an SCN-susceptible soybean cultivar before challenging it with the nematodes. Our results suggest that stimulation of these pathways prior to infection by nematodes causes a reduction in the infection. Overall there appears to be interactions and coordination between the different defense signaling pathways to ward off the invading pathogen.