Comparative Transcriptome of Contrasting Wild Arachis Genotypes Unravels NBS-LRR Genes Involved in Nematode Defense Responses

Peanut (Arachis hypogaea) is the fourth most important oil crop in the world. Among others, the Root Knot Nematode (RKN) Meloidogyne arenaria is a great constraint to peanut yield and grain quality. Transcriptome comparison of two wild Arachis species contrasting for nematode resistance, the highly resistant A. stenosperma and the moderately resistant A. duranensis, revealed differentially expressed genes (DEGs) belonging to important defense related families, including NBS-LRR genes. From the 345 NBS-LRR-encoding genes identified in the reference genome of A. duranensis, 25 were identified as significant (FDR<0.05) DEGs between nematode infected and control roots in A. stenosperma and 33 in A. duranensis. Most of these DEGs showed contrasting expression behavior between the two species, with the majority of the representatives in A. stenosperma being upregulated at 6 days after inoculation (DAI), including 12 exclusives. Phylogenetic analysis of the NBS-LRR family in A. duranensis exhibited a highly supported separation between the TIR-type and non-TIR-type clades, and a high level of sequence divergence within the clades. All A. duranensis NBS-LRR-encoding genes were duplicated, with the majority of those differentially expressed between the two species duplicated by tandem (37.4%) and scattered in most chromosomal pseudomolecules. The identification and characterization of the NBS-LRR genes responsible for RKN resistance in wild Arachis will facilitate the understanding of the molecular mechanisms of RKN resistance and genetic improvement of peanut through marker-assisted selection or gene transformation.

Financial support: Embrapa, CNPq and FAP-DF