Insights into the Structure, Function, and Ion-Mediated Signaling Pathways Transduced by Plant Integrin-Linked Kinases.

Sorina C Popescu,George V Popescu,Gizem Dimlioglu,Elizabeth K Brauer

doi:10.3389/fpls.2017.00376

Sorina C Popescu, George V Popescu + Show 2 more

Open Access

https://doi.org/10.3389/fpls.2017.00376

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Abstract

Kinases facilitate detection of extracellular signals and set in motion cellular responses for plant adaptation and survival. Some of the energy utilized for kinase signal processing is produced through the activity of ion transporters. Additionally, the synergy between cellular ions and signal transduction influences plant response to pathogens, and their growth and development. In plants, the signaling elements that connect cell wall and membrane sensors with ion homeostasis and transport-mediated processes are largely unknown. Current research indicates that plant Integrin-Linked Kinases (ILKs), a subfamily Raf-like MAP2K Kinases, may have evolved to fulfill this role. In this review, we explore new findings on plant ILKs placing a particular focus on the connection between ILKs proteins unique structural features and ILKs functions. The ankyrin repeat motifs and the kinase domains of ILKs in Arabidopsis and land plants lineage, respectively, are analyzed and discussed as potential determinants of ILKs’ metal ion cofactor specificity and their enzymatic and interaction activities. Further, ILKs regulation through gene expression, subcellular localization, and ions and ion transporters is reviewed in the context of recent studies. Finally, using evidence from literature and interactomics databanks, we infer ILKs-dependent cellular pathways and highlight their potential in transmitting multiple types of signals originating at the interface between the cell wall and plasma membrane.

Highlights

Protein kinases constitute one of the largest and most diverse enzyme families in living systems
We analyzed ILK1-like sequences in representative species of land plants, highlighting Integrin-Linked Kinases (ILKs) specific features in the ankyrin repeat (AR) and kinase domains (KDs), and summarized recent literature on the regulation of ILKs at multiple levels, and identified known and potential components of signal processing pathways mediated by ILKs
Our analysis reveals potentially new plant-specific ILK functions and places them as components in multiple signal transduction pathways, acting through a wide range of mechanisms to regulate cellular homeostasis

Summary

Introduction

Protein kinases constitute one of the largest and most diverse enzyme families in living systems. We analyzed ILK1-like sequences in representative species of land plants, highlighting ILK specific features in the ankyrin repeat (AR) and kinase domains (KDs), and summarized recent literature on the regulation of ILKs at multiple levels, and identified known and potential components of signal processing pathways mediated by ILKs. We propose a model of stresstriggered signal transduction that emphasizes the contributions of ILKs and emphasizes future exploration topics. CML9, a Ca2+ sensor, and negative PTI modulator interacted with ILK1 in vivo and inhibited ILK1 kinase activity (Brauer et al, 2016), suggesting that ILK1-CML9 are part of a putative pathway mediated by pathogen-triggered Ca2+ waves.

Results

Conclusion