Abstract
Plants elaborate a vast array of enzymes that synthesize defensive secondary metabolites in response to pathogen attack. Here, we isolated the pathogen-responsive CaMNR1 [menthone: (+)-(3S)-neomenthol reductase] gene, a member of the short-chain dehydrogenase/reductase (SDR) superfamily, from pepper (Capsicum annuum) plants. Gas chromatography-mass spectrometry analysis revealed that purified CaMNR1 and its ortholog AtSDR1 from Arabidopsis (Arabidopsis thaliana) catalyze a menthone reduction with reduced nicotinamide adenine dinucleotide phosphate as a cofactor to produce neomenthol with antimicrobial activity. CaMNR1 and AtSDR1 also possess a significant catalytic activity for neomenthol oxidation. We examined the cellular function of the CaMNR1 gene by virus-induced gene silencing and ectopic overexpression in pepper and Arabidopsis plants, respectively. CaMNR1-silenced pepper plants were significantly more susceptible to Xanthomonas campestris pv vesicatoria and Colletotrichum coccodes infection and expressed lower levels of salicylic acid-responsive CaBPR1 and CaPR10 and jasmonic acid-responsive CaDEF1. CaMNR1-overexpressing Arabidopsis plants exhibited enhanced resistance to the hemibiotrophic pathogen Pseudomonas syringae pv tomato DC3000 and the biotrophic pathogen Hyaloperonospora parasitica isolate Noco2, accompanied by the induction of AtPR1 and AtPDF1.2. In contrast, mutation in the CaMNR1 ortholog AtSDR1 significantly enhanced susceptibility to both pathogens. Together, these results indicate that the novel menthone reductase gene CaMNR1 and its ortholog AtSDR1 positively regulate plant defenses against a broad spectrum of pathogens.
Highlights
Plants elaborate a vast array of enzymes that synthesize defensive secondary metabolites in response to pathogen attack
We identified a pepper CaMNR1 gene using an array-based differential screening method (Jung and Hwang, 2000) and its putative ortholog AtSDR1 in Arabidopsis
The CaMNR1 and AtSDR1 proteins belong to the short-chain dehydrogenase/reductase (SDR) family, based on length (300 6 50 amino acids) and on conserved sequence motifs, including an N-terminal cofactor-binding domain (TGxxxGxG), a downstream structural domain (GxxDxxxNNAG) for stabilizing a central b-sheet, and a catalytic domain (YxxxK; Persson et al, 2003; Davis et al, 2005)
Summary
Plants elaborate a vast array of enzymes that synthesize defensive secondary metabolites in response to pathogen attack. Sesquiterpenoid phytoalexins, including 2,7-dihydroxycadalene, 2-hydroxy7-methoxycadalene, lacinilene C, and lacinilene C 7-methyl ether, significantly accumulate in the leaves of resistant cotton (Gossypium hirsutum) lines but not in susceptible varieties after infection by Xanthomonas campestris pv malvacearum (Essenberg et al, 1982, 1990; Pierce et al, 1996). These compounds diffuse from cells exhibiting the hypersensitive response (HR) to arrest bacterial growth in resistant plants. These findings underscore the significant roles of terpenoids in plant defense responses
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
