Identification of candidate genes involved in parasitic relationship in Orobanch aegyptiaca based on gene expression data

Broomrape (Orobanche aegyptica) is a notorious parasitic plant that cause significant production loss. Here we report analysis of publicly available RNA-seq data for broomrape, coupled with experimental verification of part of the results. After quality control of raw illumine reads, qualified reads were mapped against Orobanch transcriptome. Differential gene expression analysis, performed by using DESeq package, identified 391 differentially expressed genes between seed imbibition and haustorium attachment stages. The expression of orthologs of these genes in close relatives of Orobanch, which are parasitic, hemi- or non-parasitic, was investigated. From 391 identified genes, 87 genes showed high levels of expression in parasitic relatives and not in non-parasitic ones. Based on these analyses the 87 genes were considered as candidate genes involved in establishment of parasitic interaction between Orobanch and its host. The expression of nine of these genes were checked experimentally in flower tissues of Orobanch and in tissues sampled from the attachment site on the host root. The expression of Or2094, which a putative serine-carboxy peptidase, was detected only in the attachment site, supporting the role of this gene in establishment of the parasitic interaction. The results of this work will pave the way for future genetic engineering projects to use host-induced gene silencing strategy to enhance resistance to Orobanch in host crop plants.