A Study of Gene Expression in the Nematode Resistant Wild Peanut Relative, Arachis stenosperma, in Response to Challenge with Meloidogyne arenaria

Peanut (Arachis hypogaea) is amongst the most important legume crops in the world. One of its main yield constraints is the root-knot nematode Meloidogyne arenaria. A number of wild Arachis species, including A. stenosperma, are resistant to nematodes, and are a potential source of new resistance alleles for cultivated peanut. Using in silico subtraction of ESTs and macroarray analysis, we identified genes differentially expressed in A. stenosperma roots during its resistance response to M. arenaria. The three most differentially expressed genes [Auxin Repressed Protein (AsARP), Cytokinin Oxidase (AsCKX) and Metallothionein Type 2 (AsMET2)] were further analyzed using northern-blot and showed distinct expression profiles in the resistant A. stenosperma and susceptible A. hypogaea, both after, and sometimes even before, challenge with nematodes. Of the three most differentially expressed genes, AsARP and AsCKX are potentially involved in plant hormonal balance, and AsMET2 may be related to the reactive oxygen reaction triggered by the hypersensitive response (HR).