Virus-Induced Necrosis Is a Consequence of Direct Protein-Protein Interaction between a Viral RNA-Silencing Suppressor and a Host Catalase  

Abstract

Many plant host factors are known to interact with viral proteins during pathogenesis, but how a plant virus induces a specific disease symptom still needs further research. A lily strain of Cucumber mosaic virus (CMV-HL) can induce discrete necrotic spots on infected Arabidopsis (Arabidopsis thaliana) plants; other CMV strains can induce similar spots, but they are not as distinct as those induced by CMV-HL. The CMV 2b protein (2b), a known RNA-silencing suppressor, is involved in viral movement and symptom induction. Using in situ proximity ligation assay immunostaining and the protoplast assays, we report here that CMV 2b interacts directly with Catalase3 (CAT3) in infected tissues, a key enzyme in the breakdown of toxic hydrogen peroxide. Interestingly, CAT3, normally localized in the cytoplasm (glyoxysome), was recruited to the nucleus by an interaction between 2b and CAT3. Although overexpression of CAT3 in transgenic plants decreased the accumulation of CMV and delayed viral symptom development to some extent, 2b seems to neutralize the cellular catalase contributing to the host defense response, thus favoring viral infection. Our results thus provide evidence that, in addition to altering the type of symptom by disturbing microRNA pathways, 2b can directly bind to a host factor that is important in scavenging cellular hydrogen peroxide and thus interfere specifically with that host factor, leading to the induction of a specific necrosis.Cucumber mosaic virus (CMV) belongs to the genus Cucumovirus and contains tripartite, single-stranded sense RNAs designated RNA1 to RNA3 in decreasing order of molecular mass. RNA1 and RNA2 encode replicase proteins 1a and 2a, respectively, and RNA3 encodes the movement protein 3a. A subgenomic RNA,

Two Cytoplasmic Effectors of Phytophthora sojae Regulate Plant Cell Death via Interactions with Plant Catalases

“…Interestingly, it has also been shown that the cucumber mosaic virus (CMV) 2b protein interferes directly with plant catalase activity to induce PCD, which appears to promote CMV infection (Inaba et al, 2011). Similar to the 2b protein, we show that PsCRN63 induces PCD by promoting H 2 O 2 accumulation.…”

Oxylipin Biosynthesis Genes Positively Regulate Programmed Cell Death during Compatible Infections with the Synergistic Pair Potato Virus X-Potato Virus Y and Tomato Spotted Wilt Virus

“…Recent studies of gene expression profiles in various pathosystems have shown that sets of defense-related genes are expressed upon the infection of susceptible plants with several different viruses (3,4), suggesting that even susceptible plants recognize virus infection and mount defense responses. The discovery of coordinated induction of defense-related genes in compatible plant-virus interactions has led to investigation of the effects of their induced expression on virus accumulation and symptomatology (5,6,7). These alterations in defense gene expression might not necessarily provide a line of defense against virus infection but may have adverse effects on host metabolism that contribute to disease symptom development.…”

Modulation of host plant immunity by Tobamovirus proteins

“…Accumulation of ROS was also observed during viral compatible interactions (Riedle-Bauer, 2000;Love et al, 2005;Inaba et al, 2011;Manacorda et al, 2013). Moreover, in some plantvirus interactions, necrotic symptoms are associated with an increase of hydrogen peroxide (H 2 O 2 ) production (Inaba et al, 2011;Manacorda et al, 2013). Following this line of evidence, it was observed that a TMV-Cg mutated strain, carrying a truncated version of CgCP, induced reactive oxidative bursts that led to necrotic phenotypes in arabidopsis and tobacco plants (Kurihara and Watanabe, 2004).…”

“…Accumulation of ROS in the apoplast/cell wall compartments takes place early after the activation of the hypersensitive response (HR) (Sagi and Fluhr, 2001). Accumulation of ROS was also observed during viral compatible interactions (Riedle-Bauer, 2000;Love et al, 2005;Inaba et al, 2011;Manacorda et al, 2013). Moreover, in some plantvirus interactions, necrotic symptoms are associated with an increase of hydrogen peroxide (H 2 O 2 ) production (Inaba et al, 2011;Manacorda et al, 2013).…”