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

The 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. [ABSTRACT FROM AUTHOR]