title: Root iTRAQ protein profile analysis of two Citrus species differing in aluminum-tolerance in response to long-term aluminum-toxicity.
abstract: BACKGROUND
  Limited information is available on aluminum (Al)-toxicity-responsive proteins in woody plant roots. Seedlings of 'Xuegan' (Citrus sinensis) and 'Sour pummelo' (Citrus grandis) were treated for 18 weeks with nutrient solution containing 0 (control) or 1.2 mM AlCl3 · 6H2O (+Al). Thereafter, we investigated Citrus root protein profiles using isobaric tags for relative and absolute quantification (iTRAQ). The aims of this work were to determine the molecular mechanisms of plants to deal with Al-toxicity and to identify differentially expressed proteins involved in Al-tolerance.
  
  
  RESULTS
  C. sinensis was more tolerant to Al-toxicity than C. grandis. We isolated 347 differentially expressed proteins from + Al Citrus roots. Among these proteins, 202 (96) proteins only presented in C. sinensis (C. grandis), and 49 proteins were shared by the two species. Of the 49 overlapping proteins, 45 proteins were regulated in the same direction upon Al exposure in the both species. These proteins were classified into following categories: sulfur metabolism, stress and defense response, carbohydrate and energy metabolism, nucleic acid metabolism, protein metabolism, cell transport, biological regulation and signal transduction, cell wall and cytoskeleton metabolism, and jasmonic acid (JA) biosynthesis. The higher Al-tolerance of C. sinensis may be related to several factors, including: (a) activation of sulfur metabolism; (b) greatly improving the total ability of antioxidation and detoxification; (c) up-regulation of carbohydrate and energy metabolism; (d) enhancing cell transport; (e) decreased (increased) abundances of proteins involved in protein synthesis (proteiolysis); (f) keeping a better balance between protein phosphorylation and dephosphorylation; and (g) increasing JA biosynthesis.
  
  
  CONCLUSIONS
  Our results demonstrated that metabolic flexibility was more remarkable in C. sinenis than in C. grandis roots, thus improving the Al-tolerance of C. sinensis. This provided the most integrated view of the adaptive responses occurring in Al-toxicity roots.
authors.affiliation: Institute of Plant Nutritional Physiology and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. jianghx@163.com.|College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. jianghx@163.com.
authors.forename: Huan-Xin
authors.initials: HX
authors.lastname: Jiang
authors.affiliation: Institute of Plant Nutritional Physiology and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. talstoy@sina.com.|College of Resource and Environmental Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. talstoy@sina.com.
authors.forename: Lin-Tong
authors.initials: LT
authors.lastname: Yang
authors.affiliation: Institute of Materia Medica, Fujian Academy of Medical Sciences, Fuzhou, 350001, China. qiyiping2008@hotmail.com.
authors.forename: Yi-Ping
authors.initials: YP
authors.lastname: Qi
authors.affiliation: Institute of Plant Nutritional Physiology and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. 87312797@qq.com.|College of Resource and Environmental Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. 87312797@qq.com.
authors.forename: Yi-Bin
authors.initials: YB
authors.lastname: Lu
authors.affiliation: Institute of Plant Nutritional Physiology and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. hzrapaul@126.com.|College of Resource and Environmental Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. hzrapaul@126.com.
authors.forename: Zeng-Rong
authors.initials: ZR
authors.lastname: Huang
authors.affiliation: Institute of Plant Nutritional Physiology and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. lisongchen2002@hotmail.com.|College of Resource and Environmental Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. lisongchen2002@hotmail.com.|The Higher Educational Key Laboratory of Fujian Province for Soil Ecosystem Health and Regulation, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. lisongchen2002@hotmail.com.|Fujian Key Laboratory for Plant Molecular and Cell Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. lisongchen2002@hotmail.com.
authors.forename: Li-Song
authors.initials: LS
authors.lastname: Chen
mesh_terms: D000535:Aluminum / Q000378:metabolism / Q000633:toxicity*; D032084:Citrus sinensis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects* / Q000378:metabolism* / Q000502:physiology; D040901:Proteomics; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development; D013045:Species Specificity; D053719:Tandem Mass Spectrometry; D013997:Time Factors; D059467:Transcriptome / Q000187:drug effects
chemical_list: D010940:Plant Proteins; D000535:Aluminum