Multi-targeted trehalose-6-phosphate phosphatase I harbors a novel peroxisomal targeting signal 1 and is essential for flowering and development

Amr R A Kataya,Behzad Heidari,Ahmed Elshobaky,Jay J Thelen,Cathrine Lillo,Nemie-Feyissa Dugassa

doi:10.1007/s00425-020-03389-z

Abstract

Main conclusionThis work reveals information about new peroxisomal targeting signals type 1 and identifies trehalose-6-phosphate phosphatase I as multitargeted and is implicated in plant development, reproduction, and stress response.A putative, non-canonical peroxisomal targeting signal type 1 (PTS1) Pro-Arg-Met > was identified in the extreme C-terminus of trehalose-6-phosphate phosphatase (TPP)I. TPP catalyzes the final step of trehalose synthesis, and the enzyme was previously characterized to be nuclear only (Krasensky et al. in Antioxid Redox Signal 21(9):1289–1304, 2014). Here we show that the TPPI C-terminal decapeptide ending with Pro-Arg-Met > or Pro-Lys-Met > can indeed function as a PTS1. Upon transient expression in two plant expression systems, the free C- or N-terminal end led to the full-length TPPI targeting to peroxisomes and plastids, respectively. The nucleus and nucleolus targeting of the full-length TPPI was observed in both cases. The homozygous T-DNA insertion line of TPPI showed a pleiotropic phenotype including smaller leaves, shorter roots, delayed flowering, hypersensitivity to salt, and a sucrose dependent seedling development. Our results identify novel PTS1s, and TPPI as a protein multi-targeted to peroxisomes, plastids, nucleus, and nucleolus. Altogether our findings implicate an essential role for TPPI in development, reproduction, and cell signaling.

Highlights

Knowledge of the localization of enzymes, metabolites, and regulators is crucial for understanding their cellular function
The major targeting signal that is responsible for the localization of nuclear-encoded peroxisomal proteins is the peroxisomal targeting signal type 1 (PTS1) (Reumann 2004)
PRM > was not previously described as a PTS1 and seems to be a non-canonical signal because it is only present at the C-terminus of TPPI in all of the Arabidopsis proteome (Fig. 1)

Summary

Introduction

Knowledge of the localization of enzymes, metabolites, and regulators is crucial for understanding their cellular function. Subcellular localization of metabolic pathways is one of the principal forms of regulation and is still an ongoing endeavor in plants. The subcellular localization of major metabolic pathways is established, bypass or. Peroxisomes have specialized carriers for transport of cofactors such as NAD+, ADP, and AMP (Bernhardt et al 2012), and pore-forming, anion-selective channels facilitate the diffusion of carboxylic acids (Hu et al 2012). Transport of trehalose and trehalose-6-phosphate (T6P) has to our knowledge not been studied, but it possibly occurs through active transporters as well as by facilitated or regular diffusion, depending upon the organelle. At least, is a candidate to diffuse across the peroxisomal membrane since this membrane is assumed to allow free diffusion of molecules up to 300–400 Da and shares a common pool of small metabolites with the cytoplasm (Antonenkov and Hiltunen 2012)

Methods

Results

Discussion

Conclusion