Conditions within the endoplasmic reticulum (ER) influence most secretory proteins that pass through the ER. Therefore, eukaryotic cells must strike a balance between the ER stress response, which changes the conditions in the ER, and other considerations associated with protein secretion. Here, an interaction between the ER stress and defence responses in rice is described. Expression of OsWRKY45, which encodes a transcription factor that plays a central role in defence mediated by salicylic acid (SA), is induced by ER stress. Additionally, expression of some genes encoding pathogenesis-related (PR) secretory proteins is reduced by the ER stress response mediated by the stress sensor IRE1. Concomitant activation of the SA and ER stress responses suppresses the induction of ER stress-responsive genes, with the exception of OsWRKY45, and the reduction of PR gene expression. These findings demonstrate a functional integration between the defence and ER stress responses in plants.

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