Research article Characterization of the expression profile of a wheat aci-reductone-dioxygenase-like gene in response to stripe rust pathogen infection and abiotic stresses Liangsheng Xu a , Jianguang Jia b , Jie Lv b , Xiaofei Liang b , Dejun Han c , Lili Huang b , Zhensheng Kang a, b, * a College of Life Sciences and Shaanxi Key Laboratory of Molecular Biology for Agriculture, Northwest A & F University, Yangling, 712100 Shaanxi, PR China b College of Plant Protection, Northwest A & F University, Yangling, 712100 Shaanxi, PR China c College of Agronomy, Northwest A & F University, Yangling, 712100 Shaanxi, PR China article info Article history: Received 3 July 2009 Accepted 5 March 2010 Available online 16 March 2010 Keywords: Aci-reductone-dioxygenase (ARD) Stripe rust Abiotic stress Expression profile abstract The methionine salvage pathway is conserved from prokaryotes to high eukaryotes. The reaction cata- lyzed by aci-reductone-dioxygenase (ARD) represents a branch point in the methionine salvage pathway. A novel aci-reductone-dioxygenase gene, designed as TaARD, was identified in a subtraction library constructed with RNA isolated from wheat leaves infected with the stripe rust pathogen. TaARD was predicted to encode a 197 amino acid protein that belongs to the cupin superfamily. In transient expression assays with onion epidermal cells, the TaARD-GFP fusion protein localized to the nucleus and cytoplasm. Southern blot analysis showed that the wheat genome had multiple copies of TaARD. Quantitative real-time RT-PCR (qRT-PCR) analyses revealed that the TaARD transcript was induced in wheat leaves infected with a compatible stripe rust strain. However, its expression was reduced or suppressed in incompatible interactions and by ABA, ethephon (ET), or salicylic acid (SA) treatments. With methyl jasmonate (MeJA) treatment, TaARD transcript level was suppressed in the first 6 h but increased afterwards. The expression of TaARD also was inhibited by wounding and environmental stimuli, including high salinity and low temperature. Because of the role of ARD in the methionine salvage pathway, these results suggest that TaARD may be involved in ethylene synthesis and ethylene signaling in response to biotic and abiotic stresses. Ó 2010 Elsevier Masson SAS. All rights reserved. 1. Introduction Plants have developed a sophisticated detection and defense system to protect them against pathogen invasion. The production of ethylene is one of the earliest responses of plants to pathogen attack, and ethylene seems to be associated with defense reaction by regulating a wide range of defense-related genes, including those encoding pathogenesis-related (PR) proteins, such as chiti- nase and osmotin [1e4]. However, ethylene may also promote disease symptom development depending on the conditions and the plantepathogen combination [5,6]. S-adenosylmethionine (SAM) is one of the precursors for the biosynthesis of ethylene and polyamines (PAs) [7e9]. Based on the ethylene biosynthetic pathway, the first committed step of ethylene biosynthesis is the conversion of SAM to ACC by ACC synthase (S-adenosyl-L-methionine methylthioadenosine-lyase, EC 4.4.14) [10]. In this reaction, ACC synthase (ACS) also produces 5 0 - methylthioadenosine (MTA), which can be converted back to methionine. This methionine salvage pathway ensures a high level of ethylene production even when the pool of free methionine is relatively small. The methionine salvage cycle exists not only in plants but also in bacteria, archeae and animals. In recent years, several enzymes involved in this pathway have been well characterized at the biochemical and molecular levels [11,12]. The aci-reductone- dioxygenase (ARD) catalyzes the reaction of aci-reductone with dioxygen to produce the immediate precursor of methionine, 2-keto-4-methylthiobutyrate and formate. ARD is a unique enzyme with two different enzymatic activities, depending on the metal ion bound to it as the cofactor [13]. Fe-ARD catalyzes the methi- onine cycle reaction whereas Ni-ARD catalyzes an off-pathway Abbreviations: GFP, green fluorescent protein; SA, salicylic acid; ET, ethylene; JA, jasmonate; ABA, abscisic acid; RT-PCR, reverse transcription-polymerase chain reaction; qRT-PCR, quantitative real-time-PCR; hpi, hours post inoculation; hpt, hours post treatment; SSH, suppression subtractive hybridization; BLAST, basic local alignment search tool; PEG, polyethylene glycol; RACE, rapid amplified cloning end; ACS, 1-aminocyclopropane-1-carboxylic acid synthase; PAs, polyamines. * Corresponding author at: College of Plant Protection, Northwest A & F Univer- sity, Yangling, 712100 Shaanxi, PR China. E-mail address: kangzs@nwsuaf.edu.cn (Z. Kang). Contents lists available at ScienceDirect Plant Physiology and Biochemistry journal homepage: www.elsevier.com/locate/plaphy 0981-9428/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.plaphy.2010.03.002 Plant Physiology and Biochemistry 48 (2010) 461e468