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

Abscisic acid (ABA) is a crucial phytohormone involved in plant growth and stress responses. While the transcriptional regulation triggered by ABA is well-documented, its effects on translational regulation have been less studied. Through Ribo-seq and RNA-seq analyses, we find that ABA treatment not only influences gene expression at the mRNA level but also significantly impacts mRNA translation efficiency (TE) in Arabidopsis thaliana. ABA inhibits global mRNA translation via its core signaling pathway, which includes ABA receptors, protein phosphatase 2Cs (PP2Cs), and SNF1-related protein kinase 2 s (SnRK2s). Upon ABA treatment, Glycine-rich RNA-binding proteins 7 and 8 (GRP7&8) protein levels decrease due to both reduced mRNA level and decreased TE, which diminishes their association with polysomes and leads to a global decline in mRNA TE. The absence of GRP7&8 results in a global impairment of ABA-regulated translational changes, linking ABA signaling to GRP7-dependent modulation of mRNA translation. The regulation of GRP7 on TE relies significantly on its direct binding to target mRNAs. Moreover, mRNA translation efficiency under drought stress is partially dependent on the ABA-GRP7&8 pathways. Collectively, our study reveals GRP7's role downstream of SnRK2s in mediating translation regulation in ABA signaling, offering a model for ABA-triggered multi-route regulation of environmental adaptation.