title: Comparative proteomic and metabolomic profiling of citrus fruit with enhancement of disease resistance by postharvest heat treatment.
abstract: BACKGROUND
  From field harvest to the consumer's table, fresh citrus fruit spends a considerable amount of time in shipment and storage. During these processes, physiological disorders and pathological diseases are the main causes of fruit loss. Heat treatment (HT) has been widely used to maintain fruit quality during postharvest storage; however, limited molecular information related to this treatment is currently available at a systemic biological level.
  
  
  RESULTS
  Mature 'Kamei' Satsuma mandarin (Citrus unshiu Marc.) fruits were selected for exploring the disease resistance mechanisms induced by HT during postharvest storage. Proteomic analyses based on two-dimensional gel electrophoresis (2-DE), and metabolomic research based on gas chromatography coupled to mass spectrometry (GC-MS), and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) were conducted. The results show resistance associated proteins were up-regulated in heat treated pericarp, such as beta-1, 3-glucanase, Class III chitinase, 17.7 kDa heat shock protein and low molecular weight heat-shock protein. Also, redox metabolism enzymes were down-regulated in heat treated pericarp, including isoflavone reductase, oxidoreductase and superoxide dismutase. Primary metabolic profiling revealed organic acids and amino acids were down-regulated in heat treated pericarp; but significant accumulation of metabolites, including tetradecanoic acid, oleic acid, ornithine, 2-keto-d-gluconic acid, succinic acid, turanose, sucrose, galactose, myo-inositol, glucose and fructose were detected. Noticeably, H2O2 content decreased, while, lignin content increased in heat treated pericarp compared to the control, which might increase fruit resistibility in response to external stress. Also, flavonoids, substances which are well-known to be effective in reducing external stress, were up-regulated in heat treated pericarp.
  
  
  CONCLUSIONS
  This study provides a broad picture of differential accumulation of proteins and metabolites in postharvest citrus fruit, and gives new insights into HT improved fruit disease resistance during subsequent storage of 'Kamei' Satsuma mandarin. Interpretation of the data for the proteins and metabolites revealed reactive oxygen species (ROS) and lignin play important roles in heat treatment induced fruit resistance to pathogens and physiological disorders.
authors.affiliation: Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei, 430070, P,R, China.
authors.forename: Ze
authors.initials: Z
authors.lastname: Yun
authors.forename: Huijun
authors.initials: H
authors.lastname: Gao
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
authors.forename: Shuzhen
authors.initials: S
authors.lastname: Liu
authors.forename: Tao
authors.initials: T
authors.lastname: Luo
authors.forename: Shuai
authors.initials: S
authors.lastname: Jin
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xu
authors.forename: Juan
authors.initials: J
authors.lastname: Xu
authors.forename: Yunjiang
authors.initials: Y
authors.lastname: Cheng
authors.forename: Xiuxin
authors.initials: X
authors.lastname: Deng
mesh_terms: D002957:Citrus / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D060467:Disease Resistance; D005519:Food Preservation; D061353:Food Storage; D005638:Fruit / Q000737:chemistry / Q000254:growth & development* / Q000276:immunology / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006358:Hot Temperature; D055432:Metabolomics; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology* / Q000517:prevention & control; D010940:Plant Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D040901:Proteomics
chemical_list: D010940:Plant Proteins