Unveiling the regulatory role of GRP7 in ABA signal-mediated mRNA translation efficiency regulation

Abstract

Abscisic acid (ABA) is a crucial phytohormone involved in plant growth and stress responses. Although ABA has been implicated in the regulation of translation efficiency in Arabidopsis thaliana, the underlying mechanism remains largely unknown. In this study, we discovered that ABA treatment modulates globally translation efficiency (TE) by affecting pre-rRNA processing in the nucleolus and ribosome distribution status in the cytoplasm. The regulation of TE by ABA was largely abolished in mutants of ABA signaling core components, such as receptors PYRABACTIN RESISTANCE1/PYRABACTIN-LIKE/REGULATORY COMPONENTS OF ABA RECEPTORS (PYR/PYL/RACRs), the protein phosphatase 2Cs (PP2Cs), and the SNF1-related protein kinase 2s (SnRK2s). ABA treatment reduced the protein levels of glycine-rich RNA binding protein 7 (GRP7) in the signaling core components-dependent manner. Ribo-seq and CLIP-seq analyses unveiled GRP7s role in governing the TE of a substantial proportion of ABA-regulated genes, although independent of directly binding to the respective mRNAs. Furthermore, GRP7 directly bound to pre-rRNA and interacted with Ribosomal protein S6 (RPS6A), RPS14A and RPL36aA in the nucleolus to regulate rRNA processing. Additionally, GRP7 associated with mature polysome in the cytoplasm and is hypersensitive to translation inhibitor anisomycin when loss of function. Collectively, our study unveils the role of GRP7 in mediating translation regulation in ABA signaling, providing a novel regulatory model for plants to response to environmental stresses.