Journal Article

Protein phosphatase 2A promotes stomatal development by stabilizing SPEECHLESS in Arabidopsis

Bian, Chao, Guo, Xiaoyu, Xu, Tongda, Wang, Lu, DeLong, Alison, Zhang, Yi, Dong, Juan

2020

Overview

Stomatal guard cells control gas exchange that allows plant photosynthesis but limits water loss from plants to the environment. In Arabidopsis, stomatal development is mainly controlled by a signaling pathway comprising peptide ligands, membrane receptors, a mitogen-activated protein kinase (MAPK) cascade, and a set of transcription factors. The initiation of the stomatal lineage requires the activity of the bHLH transcription factor SPEECHLESS (SPCH) with its partners. Multiple kinases were found to regulate SPCH protein stability and function through phosphorylation, yet no antagonistic protein phosphatase activities have been identified. Here, we identify the conserved PP2A phosphatases as positive regulators of Arabidopsis stomatal development. We show that mutations in genes encoding PP2A subunits result in lowered stomatal production in Arabidopsis. Genetic analyses place the PP2A function upstream of SPCH. Pharmacological treatments support a role for PP2A in promoting SPCH protein stability. We further find that SPCH directly binds to the PP2A-A subunits in vitro. In plants, nonphosphorylatable SPCH proteins are less affected by PP2A activity levels. Thus, our research suggests that PP2A may function to regulate the phosphorylation status of the master transcription factor SPCH in stomatal development.

• Publisher: National Academy of Sciences
• Subject: Arabidopsis / Arabidopsis - physiology / Arabidopsis Proteins - antagonists & inhibitors / Arabidopsis Proteins - genetics / Arabidopsis Proteins - isolation & purification / Arabidopsis Proteins - metabolism / Basic Helix-Loop-Helix Transcription Factors - metabolism / Biological Sciences / Drug therapy / Gas exchange / Gene Expression Regulation, Plant - drug effects / Gene Expression Regulation, Plant - physiology / Genetic analysis / Guard cells / Helix-loop-helix proteins (basic) / Kinases / MAP kinase / Membrane proteins / Mutation / Nicotiana - genetics / Phosphatase / Phosphoprotein phosphatase / Phosphorylation / Phosphorylation - physiology / Photosynthesis / Plant Biology / Plant Stomata - drug effects / Plant Stomata - growth & development / Plants, Genetically Modified / Protein kinase / Protein phosphatase / Protein Phosphatase 2 - antagonists & inhibitors / Protein Phosphatase 2 - genetics / Protein Phosphatase 2 - isolation & purification / Protein Phosphatase 2 - metabolism / Protein Stability - drug effects / Proteins / Recombinant Proteins - genetics / Recombinant Proteins - isolation & purification / Recombinant Proteins - metabolism / Regulators / Signal transduction / Stability / Stomata / Transcription factors / Water loss