Auxin Signaling in Regulation of Plant Translation Reinitiation

Abstract

The mRNA translation machinery directs protein production, and thus cell growth, according to prevailing cellular and environmental conditions. The target of rapamycin (TOR) signaling pathway—a major growth-related pathway—plays a pivotal role in optimizing protein synthesis in mammals, while its deregulation triggers uncontrolled cell proliferation and the development of severe diseases. In plants, several signaling pathways sensitive to environmental changes, hormones, and pathogens have been implicated in post-transcriptional control, and thus far phytohormones have attracted most attention as TOR upstream regulators in plants. Recent data have suggested that the coordinated actions of the phytohormone auxin, Rho-like small GTPases (ROPs) from plants, and TOR signaling contribute to translation regulation of mRNAs that harbor upstream open reading frames (uORFs) within their 5′-untranslated regions (5′-UTRs). This review will summarize recent advances in translational regulation of a specific set of uORF-containing mRNAs that encode regulatory proteins—transcription factors, protein kinases and other cellular controllers—and how their control can impact plant growth and development.

RETRACTED ARTICLE: Sulfur availability regulates plant growth via glucose-TOR signaling

“…Xiong et al coined the term glucose-TOR (Glc-TOR) signaling to describe control of TOR activity by glucose through glycolysis and mitochondrial bioenergetics to regulate meristem activation. Recent reviews describe the role of plant TOR in autophagy regulation, auxin sensing, development, and nutrient sensing 17 – 20 .…”

Metabolite Control of Translation by Conserved Peptide uORFs: The Ribosome as a Metabolite Multisensor

“…Reinitiation is enhanced by TOR kinase activity, which activates eIF3h via S6 kinase1 (S6K1). TOR kinase in turn can be regulated by multiple factors, including hormones and energy, and nutrient availability (Schepetilnikov et al, 2013;Schepetilnikov and Ryabova, 2017).…”

“…For example, in AUXIN RESPONSE FACTOR (ARF) transcripts, uORFs regulate the translation of the mORF depending on auxin levels. Such reinitiation is stimulated by auxin activation of TOR activity (Schepetilnikov et al, 2013;Schepetilnikov and Ryabova, 2017).…”

Cell cycle control by the target of rapamycin signalling pathway in plants

“…It was shown that auxin signalling is relayed to TOR through Rho-related protein 2 (ROP2; a member of the Rho GTPase family; Li et al, 2017;Schepetilnikov et al, 2017). TOR activation promotes cell cycle entry by activating E2FA and E2FB transcription factors (Li et al, 2017).…”

“…TOR activation promotes cell cycle entry by activating E2FA and E2FB transcription factors (Li et al, 2017). The auxin induced ROP2-TOR pathway also plays important role in gene-specific translational control (Schepetilnikov et al, 2017;Schepetilnikov and Ryabova, 2017). The translationally controlled root and shoot meristem development and cell cycle target mRNAs by TOR are not yet established.…”