SIPK conditions transcriptional responses unique to either bacterial or oomycete elicitation in tobacco

SUMMARYThe mitogen‐activated protein kinase, SIPK (salicylic acid‐induced protein kinase), is known to be rapidly activated in tobacco (Nicotiana tabacum) by various elicitors. However, SIPK activation induced by the oomycete elicitor, β‐megaspermin, is reported to require external calcium influx, whereas that induced by the bacterial elicitor, hrpZPsph, does not. This suggests that SIPK activation is involved in different elicitor‐initiated signalling pathways, and raises the question of whether the role(s) of SIPK in mediating stress outcomes, including transcriptional re‐programming, differs in an elicitor‐specific manner. To examine this, we compared the impact of silencing SIPK on the transcript profile of tobacco suspension culture cells challenged with either hrpZPsph or β‐megaspermin. SIPK‐silencing was found to have a substantial impact on both hrpZPsph‐ and β‐megaspermin‐induced transcriptional responses, and these impacts included both common and elicitor‐differentiated features. As well as revealing a role for SIPK in modulating expression of known redox‐ and defence‐related genes in response to both elicitors, our analysis detected a substantial impact of SIPK silencing on transcription of 80S ribosomal subunit mRNAs. This novel observation suggests that SIPK may play a role in affecting translation efficiency as one mechanism for enacting rapid genome‐wide, elicitor‐specific physiological reprogramming during defence responses.