Summary: | The type-B authentic response regulators (type-B ARRs) are positive regulators of cytokinin signaling and involved in plant growth and stress responses. In this study, we used bioinformatics, RNA-seq, and qPCR to study the phylogenetic and expression pattern of 35 type-B ARRs in <i>Brassica napus</i>. The BnARRs experienced gene expansion and loss during genome polyploidization and were classified into seven groups. Whole-genome duplication (WGD) and segmental duplication were the main forces driving <i>type-B ARR</i> expansion in <i>B. napus</i>. Several <i>BnARRs</i> with specific expression patterns during rapeseed development were identified, including <i>BnARR12/14/18/23/33</i>. Moreover, we found the <i>type-B BnARRs</i> were involved in rapeseed development and stress responses, through participating in cytokinin and ABA signaling pathways. This study revealed the origin, evolutionary history, and expression pattern of type-B ARRs in <i>B. napus</i> and will be helpful to the functional characterization of BnARRs.
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