From filaments to function: The role of the plant actin cytoskeleton in pathogen perception, signaling and immunity

Abstract

The eukaryotic actin cytoskeleton is required for numerous cellular processes, including cell shape, development and movement, gene expression and signal transduction, and response to biotic and abiotic stress. In recent years, research in both plants and animal systems have described a function for actin as the ideal surveillance platform, linking the function and activity of primary physiological processes to the immune system. In this review, we will highlight recent advances that have defined the regulation and breadth of function of the actin cytoskeleton as a network required for defense signaling following pathogen infection. Coupled with an overview of recent work demonstrating specific targeting of the plant actin cytoskeleton by a diversity of pathogens, including bacteria, fungi and viruses, we will highlight the importance of actin as a key signaling hub in plants, one that mediates surveillance of cellular homeostasis and the activation of specific signaling responses following pathogen perception. B4ased on the studies highlighted herein, we propose a working model that posits changes in actin filament organization is in and of itself a highly specific signal, which induces, regulates and physically directs stimulus-specific signaling processes, most importantly, those associated with response to pathogens.

Capping Protein Modulates Actin Remodeling in Response to Reactive Oxygen Species during Plant Innate Immunity

“…Emerging evidence demonstrates a critical role for the actin cytoskeleton during plant innate immunity (Li et al, 2015a;Porter and Day, 2016). In Arabidopsis epidermal cells, the density of cortical actin filament arrays increases within minutes after infection with pathogenic and nonpathogenic bacteria as well as elicitation by diverse MAMPs (Henty-Ridilla et al, 2013bLi et al, 2015b).…”

Quantification of Cytoskeletal Dynamics in Time‐Lapse Recordings

“…In plant cells, the cytoskeleton supports many central processes, such as cell division (Lipka, Herrmann, & Mueller, 2015), cell wall deposition, which is linked to anisotropic growth (Schneider, Hanak, Persson, & Voigt, 2016), and vesicular transport (Nick 2008). In plants, and other eukaryotes, the cytoskeleton is comprised of actin filaments (Porter & Day, 2016), built from globular actin subunits, and microtubules, built from α-/β-tubulin heterodimers (Amos, 2004). The term "cytoskeleton," coined before electron and live-cell microscopy were established, implies a somewhat misleading notion: instead of resembling a rigid skeleton, actin filaments and microtubules are highly dynamic structures that undergo constant switching between phases of polymerization (growing) and depolymerization (shrinking) at the expense of ATP and GTP hydrolysis, respectively (Blanchoin, Boujemaa-Paterski, Henty, Khurana, & Staiger, 2010;Desai & Mitchison, 1997).…”

The plant LIM proteins: unlocking the hidden attractions

“…actin dynamics is the prime event of cell responsiveness and was found to be regulated under various environmental cues (Porter and Day 2016). This feature was also found crucial in development and has prospects to study under various environmental-or microbe-induced morphogenetic responses.…”

“…The actin cytoskeleton exhibited various cellular functions such as cell division, cell polarity establishment, endocytosis, vesicle trafficking, gene expression and immunity (Porter and Day 2016). So any protein that can influence the actin dynamics may directly or indirectly persuade a range of such biological processes.…”