Alternative Oxidase in Resistance to Biotic Stresses: Nicotiana attenuata AOX Contributes to Resistance to a Pathogen and a Piercing-Sucking Insect But Not Manduca sexta Larvae    

Abstract

The role of the alternative respiratory pathway in the protection of plants against biotic stress was examined in transgenic tobacco (Nicotiana attenuata) plants (irAOX) silenced in the expression of ALTERNATIVE OXIDASE (AOX) gene. Wild-type and irAOX plants were independently challenged with (1) chewing herbivores (Manduca sexta), (2) piercing-sucking insects (Empoasca spp.), and (3) bacterial pathogens (Pseudomonas syringae pv tomato DC3000), showing that all these treatments can strongly elicit accumulation of AOX gene transcripts in wild-type plants. When N. attenuata chemical defenses and resistance were examined, irAOX plants showed wild-type levels of defense-related phytohormones, secondary metabolites, and resistance to M. sexta. In contrast, piercing-sucking leafhoppers (Empoasca spp.) caused more leaf damage and induced significantly higher salicylic acid levels in irAOX compared with wild-type plants in the field and/or glasshouse. Subsequently, irAOX plants accumulated lower levels of defense metabolites, 17-hydroxygeranyllinalool diterpene glycosides, caffeoylputrescine, and nicotine compared with wild-type plants under prolonged attack of Empoasca spp. in the glasshouse. Finally, an accelerated cell death phenotype was observed in irAOX plants infected with P. syringae, which correlated with higher levels of salicylic acid and hydrogen peroxide levels in pathogen-infected irAOX compared with wild-type leaves. Overall, the AOX-associated changes in phytohormone and/or redox levels appear to support the resistance of N. attenuata plants against cell piercing-sucking insects and modulate the progression of cell death in pathogen-infected tissues but are not effective against rapidly feeding specialist herbivore M. sexta.

Pipecolic acid enhances resistance to bacterial infection and primes salicylic acid and nicotine accumulation in tobacco

“…Small pathogen-triggered increases of nicotine levels have been reported previously for P. syringae pv tomato-inoculated and tobacco mosaic virus-infected tobacco. 43,44 By contrast, infection with the oomycete pathogen Phytophtora nicotianae resulted in decreased nicotine levels. 45 Whether a plant protective function of nicotine toward microbial pathogen infection exists is yet indeterminate to our knowledge, although nicotine has been demonstrated to have in vitro antimicrobial activity to several human-pathogenic fungi and bacteria.…”

Reactive oxygen species and plant resistance to fungal pathogens

“…DAB staining has been often used to visualise the generation of H 2 O 2 in planta (Asai et al, 2010;Dubreuil-Maurizi et al, 2010;Kobayashi et al, 2012;L'Haridon et al, 2011;Liao et al, 2012;Rojas et al, 2012;Simon et al, 2013;Torres et al, 2005;Yokawa et al, 2011;Zhang et al, 2012). The Amplex Red hydrogen peroxide/peroxidase activity assay also allows quantifying H 2 O 2 concentrations and consists in a non-fluorescent molecule that is oxidised by H 2 O 2 and becomes fluorescent in presence of peroxidase.…”

“…The Amplex Red hydrogen peroxide/peroxidase activity assay also allows quantifying H 2 O 2 concentrations and consists in a non-fluorescent molecule that is oxidised by H 2 O 2 and becomes fluorescent in presence of peroxidase. Recent examples of this method applied to plants are cited hereafter (Shin and Schachtman, 2004;Zhang et al, 2012). An analogous method to quantify H 2 O 2 uses 3-methylbenzothiazoline hydrazine that reacts in presence of peroxidases (Malolepsza and Rozalska, 2005).…”

The Roles of Mitochondrial Reactive Oxygen Species in Cellular Signaling and Stress Response in Plants

“…AOX has also been reported to be involved in plant defense against bacterial, viral, and fungal pathogens via regulation of ROS metabolism (Cheng et al, 2011;Lee et al, 2011;Vanlerberghe, 2012, 2013;Zhang et al, 2012). Differential expression of AOX and MnSOD transcripts at pathogen exposure and HR indicate a complex response pattern Vanlerberghe, 2012, 2013).…”