| Summary: | Hypersensitive-induced response protein (HIR) is a class of plant immune proteins that play pivotal roles in <i>Sclerotinia sclerotiorum</i> (Lib.) de Bary resistance. However, there has been no systematic investigation and identification of <i>HIR</i> genes in rapeseed (<i>Brassica napus</i> L.). Hence, we identified 50 <i>BnHIR</i> genes and classified them into four groups. Subcellular localization prediction suggested that HIR proteins are mainly localized in the mitochondria. <i>Cis</i>-acting elements involved in light and diverse abiotic stress were found in the promoter regions of <i>BnHIR</i>. The majority of <i>BnHIR</i> genes in Groups 1/3/4 were expressed in most examined tissues, especially in leaves and siliques pericarp, while the <i>BnHIR</i> genes in Group 2 were not or had low expression in all detected tissues. In the case of <i>S. sclerotiorum</i> inoculation, <i>HIR</i> genes in Groups 1/3/4 were strongly induced, especially homologous genes in Group 1, which exhibited different expression patterns. Moreover, overexpression of <i>BnHIR2.7</i> in <i>Arabidopsis thaliana</i> illustrated its prominent resistance to <i>S. sclerotiorum</i>. Our study provides insight into the evolutionary relationships of the <i>HIR</i> family genes in <i>B. napus</i> and lays the foundation for their resistance to <i>S. sclerotiorum</i> in <i>B. napus</i>.
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