title: A transcriptomic approach highlights induction of secondary metabolism in citrus fruit in response to Penicillium digitatum infection.
abstract: BACKGROUND
  Postharvest losses of citrus fruit due to green mold decay, caused by the fungus Penicillium digitaum, have a considerable economic impact. However, little is known about the molecular processes underlying the response of citrus fruit to P. digitatum.
  
  
  RESULTS
  Here we describe the construction of a subtracted cDNA library enriched in citrus genes preferentially expressed in response to pathogen infection followed by cDNA macroarray hybridization to investigate gene expression during the early stages of colonization of the fruit's peel by P. digitatum. Sequence annotation of clones from the subtracted cDNA library revealed that induction of secondary and amino acid metabolisms constitutes the major response of citrus fruits to P. digitatum infection. Macroarray hybridization analysis was conducted with RNA from either control, wounded, ethylene treated or P. digitatum infected fruit. Results indicate an extensive overlap in the response triggered by the three treatments, but also demonstrated specific patterns of gene expression in response to each stimulus. Collectively our data indicate a significant presence of isoprenoid, alkaloid and phenylpropanoid biosynthetic genes in the transcriptomic response of citrus fruits to P. digitatum infection. About half of the genes that are up-regulated in response to pathogen infection are also induced by ethylene, but many examples of ethylene-independent gene regulation were also found. Two notable examples of this regulation pattern are the genes showing homology to a caffeine synthase and a berberine bridge enzyme, two proteins involved in alkaloid biosynthesis, which are among the most induced genes upon P. digitatum infection but are not responsive to ethylene.
  
  
  CONCLUSIONS
  This study provided the first global picture of the gene expression changes in citrus fruit in response to P. digitatum infection, emphasizing differences and commonalities with those triggered by wounding or exogenous ethylene treatment. Interpretation of the differentially expressed genes revealed that metabolism is redirected to the synthesis of isoprenes, alkaloids and phenylpropanoids.
authors.affiliation: Departamento de Ciencia de los Alimentos, Instituto de Agroquímica y Tecnología de Alimentos-CSIC, Apartado de Correos 73, Burjassot, E46100-Valencia, Spain. lgonzalez@iata.csic.es
authors.forename: Luis
authors.initials: L
authors.lastname: González-Candelas
authors.forename: Santiago
authors.initials: S
authors.lastname: Alamar
authors.forename: Paloma
authors.initials: P
authors.lastname: Sánchez-Torres
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Zacarías
authors.forename: Jose F
authors.initials: JF
authors.lastname: Marcos
mesh_terms: D002957:Citrus / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D005030:Ethylenes / Q000494:pharmacology; D005638:Fruit / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D020869:Gene Expression Profiling; D010407:Penicillium / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology*
chemical_list: D005030:Ethylenes; C036216:ethylene
references.citation: Plant Cell. 1995 Jul;7(7):1085-1097
references.pmid: 12242399
references.citation: Curr Opin Immunol. 2001 Feb;13(1):63-8
references.pmid: 11154919
references.citation: FEBS Lett. 2006 Feb 13;580(4):1123-30
references.pmid: 16506311
references.citation: Plant Mol Biol. 2005 Oct;59(3):407-33
references.pmid: 16235108
references.citation: Phytochemistry. 1997 Jan;44(2):257-66
references.pmid: 9004542
references.citation: Genome Biol. 2003;4(3):R20
references.pmid: 12620105
references.citation: Trends Plant Sci. 2004 Mar;9(3):116-22
references.pmid: 15003234
references.citation: Proc Natl Acad Sci U S A. 1991 Oct 1;88(19):8821-5
references.pmid: 1681544
references.citation: Mol Plant Microbe Interact. 2000 Aug;13(8):837-46
references.pmid: 10939255
references.citation: Plant Physiol. 2002 Nov;130(3):1079-89
references.pmid: 12427975
references.citation: Proc Natl Acad Sci U S A. 2003 Jan 21;100(2):751-6
references.pmid: 12524452
references.citation: BMC Plant Biol. 2007 Feb 22;7:8
references.pmid: 17316447
references.citation: Plant Physiol. 2005 May;138(1):105-15
references.pmid: 15888683
references.citation: Phytochemistry. 2007 Jan;68(2):150-75
references.pmid: 17109902
references.citation: Annu Rev Plant Physiol Plant Mol Biol. 2001 Jun;52:29-66
references.pmid: 11337391
references.citation: J Agric Food Chem. 2004 Nov 3;52(22):6724-31
references.pmid: 15506808
references.citation: J Exp Bot. 2005 Aug;56(418):2183-93
references.pmid: 15983011
references.citation: Proc Natl Acad Sci U S A. 1996 Jun 11;93(12):6025-30
references.pmid: 8650213
references.citation: Plant Physiol. 2005 Jun;138(2):1058-70
references.pmid: 15923335
references.citation: FEBS Lett. 2001 Nov 16;508(2):215-20
references.pmid: 11718718
references.citation: Annu Rev Phytopathol. 2006;44:393-416
references.pmid: 16602950
references.citation: Annu Rev Plant Biol. 2006;57:711-38
references.pmid: 16669779
references.citation: Int Microbiol. 2004 Sep;7(3):199-206
references.pmid: 15492934
references.citation: Annu Rev Plant Physiol Plant Mol Biol. 1999 Jun;50:473-503
references.pmid: 15012217
references.citation: Mol Plant Pathol. 2008 Sep;9(5):609-31
references.pmid: 19018992
references.citation: Plant Cell. 2006 Mar;18(3):731-46
references.pmid: 16473969
references.citation: Nucleic Acids Res. 1997 Sep 1;25(17):3389-402
references.pmid: 9254694
references.citation: Folia Microbiol (Praha). 2002;47(4):375-8
references.pmid: 12422513
references.citation: Plant J. 2004 Apr;38(1):131-41
references.pmid: 15053766
references.citation: Plant Physiol. 1991 Nov;97(3):880-5
references.pmid: 16668526
references.citation: Plant Physiol. 2002 Jul;129(3):1341-51
references.pmid: 12114587
references.citation: Plant Physiol. 2004 Jan;134(1):460-9
references.pmid: 14730073
references.citation: Nature. 2001 Jun 14;411(6839):843-7
references.pmid: 11459067
references.citation: Plant Mol Biol. 2005 Feb;57(3):375-91
references.pmid: 15830128
references.citation: Phytopathology. 2007 Nov;97(11):1491-500
references.pmid: 18943520