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 2s (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.

脱落酸（Abscisic acid, ABA）是参与植物生长与胁迫响应的关键植物激素。尽管ABA介导的转录调控已有充分研究报道，但ABA对翻译调控的影响却鲜有探讨。本研究借助核糖体测序（Ribo-seq）与RNA测序（RNA-seq）分析发现，ABA处理不仅可在mRNA水平调控基因表达，还能显著改变拟南芥（Arabidopsis thaliana）的mRNA翻译效率（translation efficiency, TE）。ABA通过其核心信号通路抑制全局mRNA翻译，该通路包含ABA受体、蛋白磷酸酶2C（protein phosphatase 2Cs, PP2Cs）以及SNF1相关蛋白激酶2（SNF1-related protein kinase 2s, SnRK2s）。经ABA处理后，富含甘氨酸的RNA结合蛋白7和8（Glycine-rich RNA-binding proteins 7 and 8, GRP7&8）的蛋白水平因mRNA丰度降低与翻译效率下降共同下调，这削弱了其与多聚核糖体（polysomes）的结合，并引发全局mRNA翻译效率的整体下降。缺失GRP7&8会全面损害ABA调控的翻译变化，从而将ABA信号通路与GRP7依赖的mRNA翻译调控建立起直接关联。GRP7对翻译效率的调控在很大程度上依赖于其与靶标mRNA的直接结合。此外，干旱胁迫下的mRNA翻译效率在一定程度上依赖于ABA-GRP7&8信号通路。综上，本研究揭示了GRP7在SnRK2s下游介导ABA信号通路中翻译调控的功能，为ABA触发的环境适应多通路调控提供了全新的研究模型。