Transcriptome Profiling ofhrf2Transgenic Rapeseed Revealed Genes Related to the Defense Responses and Signaling Pathways

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Ectopic expression of the HarpinXooc–encoding genehrf2in rapeseed (Brassica napusL.) confers enhanced resistance toSclerotinia sclerotiorumand improved agronomic performance. To better understand the molecular mechanisms of harpin‐mediated plant responses, we developed a 3’–tag digital gene expression (DGE) method to compare the mRNA expression patterns of transgenic T‐4 rapeseed harboringhrf2and untransformed Yangyou 4 (Y4) at the global level. Solexa Illumina sequencing yielded 5,645,091 and 6,007,037 clean tags, corresponding to 14,237 and 14,773 genes for Y4 and T‐4, respectively. We identified 2114 differentially expressed genes (DEGs; log2 ratio ≥ 1, false discovery rate [FDR] ≤ 0.001) between transgenic T‐4 and untransformed Y4 that assigned to seven Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways and 19 Gene Ontology categories. Numerous genes related to defense responses were differentially expressed in T‐4, representing categories such as hypersensitive response, defense proteins, plant cell wall components, and phenylpropanoid metabolism pathway. Furthermore, expression was largely modified in T‐4 in signaling pathways including G protein, Ca2+, ubiquitination, protein kinase, salicylic acid, jasmonic acid, abscisic acid, ethylene, and auxin hormones. We also identified numerous DEGs encoding transcription factors in T‐4. This analysis shows the breadth of molecular mechanisms of harpin‐mediated plant responses in genetically transformed plants. Furthermore, the DGE sequence resources identified in this study provide a platform for functional genomics studies of rapeseed.