The Role of Post‐Translational Enzyme Modifications in the Metabolic Adaptations of Phosphorus‐Deprived Plants

Abstract

Post‐translational modification (PTM) is the covalent alteration of a functional group of a specific amino acid residue within a particular protein. Diverse proteinPTMsrepresent pivotal regulatory mechanisms that integrate signalling, development, gene expression, metabolism, and stress responses in plant and animal cells. ThesePTMs: (i) are often genetically predetermined, rapid, interconnected, and reversible; and (ii) can not only dramatically alter an enzyme's activity but may also generate specificPTM‐dependent docking sites that influence its interactions with other proteins. The aim of this chapter is to highlight three crucialPTMs(phosphorylation, monoubiquitination, and glycosylation) and to provide examples of their participation in thein‐vivofunction and control of several key enzymes that facilitate plant acclimatisation to soluble phosphate (Pi) ‐deficient soils. Pinpointing the impact of altered Pi supply on the prevalence, mechanisms and functions of enzymePTMswill make an important contribution to the implementation of effective biotechnological strategies for engineering crops having enhanced P‐acquisition and P‐use efficiency.

Extraction and Characterization of Extracellular Proteins and Their Post-Translational Modifications from Arabidopsis thaliana Suspension Cell Cultures and Seedlings: A Critical Review

“…Such is the case for a pair of differentially glycosylated, Pi-starvation inducible AtPAP26 glycoforms that were fully purified from the cell wall (AtPAP26-CW1 and -CW2) and secretome (AtPAP26-S1 and -S2) of Pi-deprived Arabidopsis suspension cells [87,103]. A 55 kDa protein exclusively copurified with the AtPAP26-CW2 and AtPAP26-S2 glycoforms, and was identified via MS as a curculin-like lectin [104]. Lectins are carbohydrate-binding proteins that interact with the glycan groups of glycoproteins [105,106].…”

“…Lectins are carbohydrate-binding proteins that interact with the glycan groups of glycoproteins [105,106]. Bifluorescence complementation, Far Western immunoblotting, and glycoprofile analysis by LC MS/MS all indicate that AtPAP26-CW2 and -S2 specifically associate with the curculin-like lectin, and that this interaction (which appears to stimulate their APase activity) is mediated by the unique oligosaccharide groups found on these glycoforms, highlighting the important role of glycosylation in determining a protein’s properties and function [104]. …”

“…Reversible phosphorylation is the most predominant and well-studied PTM of eukaryotic proteins [14,15,25,73,104]. Greater than 70% of all eukaryotic proteins are believed to be phosphorylated at some point during their lifetime, with the majority of these proteins having multiple phosphorylation sites [104].…”

“…Greater than 70% of all eukaryotic proteins are believed to be phosphorylated at some point during their lifetime, with the majority of these proteins having multiple phosphorylation sites [104]. Phosphoproteomics refers to the study of varying aspects of protein phosphorylation, including phosphoprotein identification, quantification, mapping of phosphorylation sites [14].…”

“…In eukaryotes, protein phosphorylation occurs predominantly on serine and threonine residues, as well as less commonly on tyrosine residues [28,110,111]. The addition or removal of a phosphoryl group (PO 3 2− ), catalyzed by protein kinases and phosphatases, respectively, alters the function and activity of proteins participating in virtually all aspects of cellular physiology and development including signal transduction, cell differentiation, disease and stress responses, and metabolic pathway flux [104,112]. Protein kinases are one of the largest gene super families in eukaryotes, with approximately 1100 different protein kinases encoded in the genome of Arabidopsis , illustrating the crucial role of protein phosphorylation in the control of diverse cellular processes [14,104,112].…”