Transformed tobacco (Nicotiana tabacum) plants over-expressing a peroxisome proliferator-activated receptor gene from Xenopus laevis (xPPARα) show increased susceptibility to infection by virulent Pseudomonas syringae pathogens

Abstract

Transgenic tobacco plants capable of over-expressing Xenopus PPARα (xPPARα), a transcription factor known to be required for peroxisome proliferation in animals, were recently generated. These plants (herewith referred to as PPAR-OE) were found to have increased peroxisome abundance, higher peroxisomal acyl-CoA oxidase and catalase activity and modified fatty acid metabolism. Further characterization of PPAR-OE plants revealed a higher susceptibility to virulent and a partial loss of resistance to avirulent Pseudomonas syringae pathogens, whereas the basal resistance response remained unaffected. Biochemical- and defense-related gene expression analyses showed that increased susceptibility to bacterial invasion coincided with the generalized reduction in H(2)O(2) and salicylic acid (SA) levels observed within the first 24 h of bacterial contact. Decreased H(2)O(2) levels were correlated with modified activity levels of catalase and other antioxidant enzymes. A correspondence between a rapid (within 1-24 hpi; ACCO and AOC) and sustained increase (up to 6 days pi; ACCO) in the expression levels of ethylene (ACCO) and jasmonic acid (AOC) biosynthetic genes and a higher susceptibility to virulent bacterial invasion was also observed in PPAR-OE plants. Conversely, no apparent differences in the short- and/or long-term expression levels of markers for the hypersensitive-response, oxidative burst and systemic-acquired resistance were observed between wild type and PPAR-OE plants. The results suggest that peroxisome proliferation could lead to increased susceptibility to bacterial pathogens in tobacco by altering the redox balance of the plant and the expression pattern of key defense signaling pathway genes.

The ability to manipulate ROS metabolism in pepper may affect aphid virulence

“…Suppression of catalase has been found to enhance ROS levels in response to biotic stress in various plant species such as tobacco 48 and sorgum 49 . Conversely, higher levels of catalase activity have been shown to increase susceptibility to pathogens 50,51 and also to M. persicae 52 . There are three main isoforms of catalases: class I, II and III 24,53 .…”

The novel and taxonomically restricted Ah24 gene from grain amaranth (Amaranthus hypochondriacus) has a dual role in development and defense

“…Arabidospis plants were grown in controlled conditions of light (photosynthetic photon flux density (PPFD) of ≈200 μmol m −2 s −1 ), photoperiod (16 h light/8 h dark) and temperature (22 ± 1°C). Tobacco plants were grown as described previously (Valenzuela-Soto et al, 2011 ).…”

The battle between pepper and aphid : Genetics and mechanism of host plant resistance

“…Suppression of catalase has been found to enhance ROS levels in response to biotic stress in various plant species such as tobacco (Takahashi et al, 1997, Yi et al, 2003 and sorgum (Zhu-Salzman et al, 2004). Conversely, higher levels of catalase activity have been shown to increase susceptibility to pathogens (Valenzuela-Soto et al, 2011, Palanisamy & Mandal, 2014 and also to M. persicae (Divol et al, 2005). There are three main isoforms of catalases: class I, II and III (Willekens et al, 1994, Mhamdi et al, 2010.…”