R. Srivastava, Z. Li, G. Russo, J. Tang, R. Bi, U. Muppirala, S. Chudalayandi, A. Severin, M. He, S. Vaitkevicius, C. Lawrence-Dill, P. Liu, A.E. Stapleton, D. Bassham, F. Brandizzi, and S. Howell (2018). Persistent ER stress in maize seedlings engages ZmIRE1 in a multiphasic process that transitions from prosurvival activities to cell death. Accepted by The Plant Cell.

Abstract

The unfolded protein response (UPR) is a highly conserved response that protectsplants from adverse environmental conditions. The UPR is elicited by endoplasmic reticulum (ER) stress, in which unfolded and misfolded proteins accumulate within the ER.In response to persistent ER stress, a multiphasic program of gene expression unfolds that is interwoven among other cellular events, including the induction of autophagy. One of the earliest phasesinvolvesthe degradation by regulated IRE1-dependent RNA degradation (RIDD) of RNA transcripts derived from a family of peroxidasegenes. RIDD results from the activation of ZmIRE1 promiscuous ribonuclease activity that attacks the mRNAs of secreted proteins. This was followed by an upsurge in expression of the canonical UPR genesindirectly driven by ZmIRE1 due to its splicing of ZmbZIP60 to make an active transcription factor that directly upregulates many of the UPR genes. At the peak of UPR gene expression, a global wave of alternative RNA splicingled to the production of many aberrant UPR gene transcripts, likely tempering the ER stress response. During later stages of ER stress, ZmIRE1’s activity declined as did the expression of survival modulatinggenes, Bax inhibitor1 and Bcl-2-associated athanogene7,amidsta rising tide of cell death. Thus, in response to persistent ER stress, maize seedlingsembark on a course of gene expression and cellular events progressing from prosurvival activities to cell death.