Actin depolymerization is able to increase plant resistance against pathogens via activation of salicylic acid signalling pathway

Abstract

The integrity of the actin cytoskeleton is essential for plant immune signalling. Consequently, it is generally assumed that actin disruption reduces plant resistance to pathogen attack. Here, we demonstrate that actin depolymerization induced a dramatic increase in salicylic acid (SA) levels in Arabidopsis thaliana . Transcriptomic analysis showed that the SA pathway was activated due to the action of isochorismate synthase (ICS). The effect was also confirmed in Brassica napus . This raises the question of whether actin depolymerization could, under particular conditions, lead to increased resistance to pathogens. Thus, we explored the effect of pretreatment with actin-depolymerizing drugs on the resistance of Arabidopsis thaliana to the bacterial pathogen Pseudomonas syringae , and on the resistance of an important crop Brassica napus to its natural fungal pathogen Leptosphaeria maculans . In both pathosystems, actin depolymerization activated the SA pathway, leading to increased plant resistance. To our best knowledge, we herein provide the first direct evidence that disruption of the actin cytoskeleton can actually lead to increased plant resistance to pathogens, and that SA is crucial to this process.

Tomato Metabolic Changes in Response to Tomato-Potato Psyllid (Bactericera cockerelli) and Its Vectored Pathogen Candidatus Liberibacter solanacearum

“…Some hormones coexist in several isoforms with differential plant defense activity. For instance, zeatin, a cytokinin known to encourage lateral growth of buds [ 37 ]), has been shown to have an isomerically differential role in plant defense against microbial pathogens, where tobacco plants treated with exogenous trans-zeatin were significantly protected from damage by the pathogenic bacterium Pseudomonas syringae , while those treated with cis-zeatin were not [ 38 ]. We can speculate that such coexistence of isoforms in different concentrations may have led to the constitutively low abundances under certain treatments in the present study.…”

Plant Cells under Attack: Unconventional Endomembrane Trafficking during Plant Defense

“…For example, in the case of P.syringae infection, the already described actin-binding effectors of P.syringae are not sufficient to prevent PEN3 relocation to the PM [56][57][58]. On the other hand, upon B. graminis attack leading to PEN3 deposition at the PM, disruption of the cytoskeleton results in more rapidly induced autophagic mechanisms that were more effective than PEN3 associated secretion for B. graminis resistance [54,59].…”

Disrupted actin: a novel player in pathogen attack sensing?

“…This fits together with the fact that a PA increase follows the recognition of MAMPs and DAMPs, but also the application of salicylic acid (SA) (Kalachova et al , 2013; Cacas et al , 2017; Gully et al , 2019). At the same time, chemical disruption of actin also triggers SA accumulation and SA‐responsive genes (Matouskova et al , 2014; Kalachova et al , 2019; Leontovycova et al , 2019). An activated SA pathway by actin disruption could even lead to increased plant resistance to pathogens (Leontovycova et al , 2019) (Fig.…”

“…At the same time, chemical disruption of actin also triggers SA accumulation and SA‐responsive genes (Matouskova et al , 2014; Kalachova et al , 2019; Leontovycova et al , 2019). An activated SA pathway by actin disruption could even lead to increased plant resistance to pathogens (Leontovycova et al , 2019) (Fig. 1c).…”