Genome wide identification of wheat and Brachypodium type one protein phosphatases and functional characterization of durum wheat TdPP1a

Abstract

Reversible phosphorylation is an essential mechanism regulating signal transduction during development and environmental stress responses. An important number of dephosphorylation events in the cell are catalyzed by type one protein phosphatases (PP1), which catalytic activity is driven by the binding of regulatory proteins that control their substrate specificity or subcellular localization. Plants harbor several PP1 isoforms accounting for large functional redundancies. While animal PP1s were reported to play relevant roles in controlling multiple cellular processes, plant orthologs remain poorly studied. To decipher the role of plant PP1s, we compared PP1 genes from three monocot species, Brachypodium, common wheat and rice at the genomic and transcriptomic levels. To gain more insight into the wheat PP1 proteins, we identified and characterized TdPP1a, the first wheat type one protein phosphatase from a Tunisian durum wheat variety Oum Rabiaa3. TdPP1a is highly conserved in sequence and structure when compared to mammalian, yeast and other plant PP1s. We demonstrate that TdPP1a is an active, metallo-dependent phosphatase in vitro and is able to interact with AtI2, a typical regulator of PP1 functions. Also, TdPP1a is capable to complement the heat stress sensitivity of the yeast mutant indicating that TdPP1a is functional also in vivo. Moreover, transient expression of TdPP1a::GFP in tobacco leaves revealed that it is ubiquitously distributed within the cell, with a strong accumulation in the nucleus. Finally, transcriptional analyses showed similar expression levels in roots and leaves of durum wheat seedlings. Interestingly, the expression in leaves is significantly induced following salinity stress, suggesting a potential role of TdPP1a in wheat salt stress response.

The Protein Phosphatases ATUNIS1 and ATUNIS2 Regulate Cell Wall Integrity in Tip-Growing Cells

“…Qin et al (2014) also found that TOPP4-GFP associates with the plasma membrane of root cells in Pro35S:TOPP4-GFP transgenic plants. A cytoplasmic and nuclear localization was also reported for the rice OsPP1a-GFP (Ogawa et al, 2011) and the wheat TdPP1a-GFP (Bradai et al, 2018). So far, all the identified components of the CWI pathway in PTs have been shown to be delivered to the plasma membrane (ANX1/2, BUPS1/2, RBOHH/J, and MRI) (Boisson-Dernier et al, 2009, 2013Ge et al, 2017) or to be associated with vesicles and the CW (LRX8, LRX9, and LRX10 [Wang et al, 2018] and possibly RALF4 and RALF19 [Ge et al, 2017]).…”

Plant protein phosphatases: What do we know about their mechanism of action?

“…The genomic organization within the clusters and the protein primary sequence is conserved. The presence of distinct PP1 isoforms may lead to functional distinction [27]. PP1c isoforms share 90.9–99.7% amino acid similarities indicating a high degree of functional redundancy among them [25].…”

“…They have highly conserved Ser/Thr phosphatase domain at the N‐terminal as well as catalytic central core domain, particularly motifs involved in microcystin inhibition docking (SAPNYC), phosphate binding (VDRG and GNHE) and metal coordination (GDxHG, DxVDRG, and GNHE). Most PP1s show ETLMCSF motif for binding PIPs except for Arabidopsis TOPP4, which has ENLMCSF motif [27]. TOPP4 directly binds DELLA proteins [32].…”

“…Ser/Thr Phosphatases PP1 phosphatases: Motifs and interacting proteins result in a big interactome PP1 phosphatases are involved in the regulation of several cellular processes in both plants and animals [12,20,25,26]. They exhibit highly conserved sequences and structure among eukaryotes with the plant and animal PP1s showing more than 70% identical residues in the core catalytic domain [23,27]. PP1 is a single-domain hub protein [28].…”

“…Nine TOPP isoforms have been reported in Arabidopsis. PP1s have been reported in rice, wheat, Brachypodium, and Vicia faba also [25,27,[31][32][33][34]. Plant PP1 proteins from wheat, rice, and Brachypodium comprise 296-354 amino acids (mol.…”