ACTIN DEPOLYMERIZING FACTOR4 Regulates Actin Dynamics during Innate Immune Signaling in Arabidopsis    

Abstract

Conserved microbe-associated molecular patterns (MAMPs) are sensed by pattern recognition receptors (PRRs) on cells of plants and animals. MAMP perception typically triggers rearrangements to actin cytoskeletal arrays during innate immune signaling. However, the signaling cascades linking PRR activation by MAMPs to cytoskeleton remodeling are not well characterized. Here, we developed a system to dissect, at high spatial and temporal resolution, the regulation of actin dynamics during innate immune signaling in plant cells. Within minutes of MAMP perception, we detected changes to single actin filament turnover in epidermal cells treated with bacterial and fungal MAMPs. These MAMP-induced alterations phenocopied an ACTIN DEPOLYMERIZING FACTOR4 (ADF4) knockout mutant. Moreover, actin arrays in the adf4 mutant were unresponsive to a bacterial MAMP, elf26, but responded normally to the fungal MAMP, chitin. Together, our data provide strong genetic and cytological evidence for the inhibition of ADF activity regulating actin remodeling during innate immune signaling. This work is the first to directly link an ADF/cofilin to the cytoskeletal rearrangements elicited directly after pathogen perception in plant or mammalian cells.

CASEIN KINASE1-LIKE PROTEIN2 Regulates Actin Filament Stability and Stomatal Closure via Phosphorylation of Actin Depolymerizing Factor

“…The Arabidopsis thaliana genome encodes 11 ADF proteins, which play important roles in various biological processes. ADF4 is involved in innate immune signaling (Tian et al, 2009;Henty-Ridilla et al, 2014); ADF7 promotes pollen tube growth ; and ADF2 is required for cell growth, development, and root-knot nematode infection (Clément et al, 2009). In addition, the 14-3-3 l protein interacts with phosphorylated ADF1 to regulate actin dynamics during hypocotyl elongation .…”

Myosins XI modulate host cellular responses and penetration resistance to fungal pathogens

“…The secretory vesicles and organelles, including peroxisomes, Golgi, mitochondria, and the nucleus, also move toward penetration sites (7,13). In addition to the deposition of cell wall reinforcements and focal accumulation of penetration-related proteins such as PEN3, the accretion of cytoplasm and organelles at sites of attempted fungal penetration involves reorganization of actin cytoskeleton, which forms a radial array focused on penetration site (10,11,(14)(15)(16)(17)(18). Consistent with this finding, disruption of AFs hampers penetration resistance, leading to increased penetration frequency by various fungal and oomycete pathogens (15)(16)(17)19).…”

Nuclear Function of Subclass I Actin-Depolymerizing Factor Contributes to Susceptibility in Arabidopsis to an Adapted Powdery Mildew Fungus

“…ADF5 and ADF9 in subclass III and ADF6 in subclass IV are expressed in a wide variety of tissues (Ruzicka et al, 2007). As in animal cells, ADFs in plants also bind to both monomeric and filamentous actins (Tian et al, 2009;Zheng et al, 2013) and regulate the organization of AFs (Zheng et al, 2013;Henty-Ridilla et al, 2014).…”