title: Harpin-induced expression and transgenic overexpression of the phloem protein gene AtPP2-A1 in Arabidopsis repress phloem feeding of the green peach aphid Myzus persicae.
abstract: BACKGROUND
  Treatment of plants with HrpNEa, a protein of harpin group produced by Gram-negative plant pathogenic bacteria, induces plant resistance to insect herbivores, including the green peach aphid Myzus persicae, a generalist phloem-feeding insect. Under attacks by phloem-feeding insects, plants defend themselves using the phloem-based defense mechanism, which is supposed to involve the phloem protein 2 (PP2), one of the most abundant proteins in the phloem sap. The purpose of this study was to obtain genetic evidence for the function of the Arabidopsis thaliana (Arabidopsis) PP2-encoding gene AtPP2-A1 in resistance to M. persicae when the plant was treated with HrpNEa and after the plant was transformed with AtPP2-A1.
  
  
  RESULTS
  The electrical penetration graph technique was used to visualize the phloem-feeding activities of apterous agamic M. persicae females on leaves of Arabidopsis plants treated with HrpNEa and an inactive protein control, respectively. A repression of phloem feeding was induced by HrpNEa in wild-type (WT) Arabidopsis but not in atpp2-a1/E/142, the plant mutant that had a defect in the AtPP2-A1 gene, the most HrpNEa-responsive of 30 AtPP2 genes. In WT rather than atpp2-a1/E/142, the deterrent effect of HrpNEa treatment on the phloem-feeding activity accompanied an enhancement of AtPP2-A1 expression. In PP2OETAt (AtPP2-A1-overexpression transgenic Arabidopsis thaliana) plants, abundant amounts of the AtPP2-A1 gene transcript were detected in different organs, including leaves, stems, calyces, and petals. All these organs had a deterrent effect on the phloem-feeding activity compared with the same organs of the transgenic control plant. When a large-scale aphid population was monitored for 24 hours, there was a significant decrease in the number of aphids that colonized leaves of HrpNEa-treated WT and PP2OETAt plants, respectively, compared with control plants.
  
  
  CONCLUSIONS
  The repression in phloem-feeding activities of M. persicae as a result of AtPP2-A1 overexpression, and as a deterrent effect of HrpNEa treatment in WT Arabidopsis rather than the atpp2-a1/E/142 mutant suggest that AtPP2-A1 plays a role in plant resistance to the insect, particularly at the phloem-feeding stage. The accompanied change of aphid population in leaf colonies suggests that the function of AtPP2-A1 is related to colonization of the plant.
authors.affiliation: Key Laboratory of Monitoring and Management of Crop Pathogens and Insect Pests, Ministry of Agriculture of R. P. China, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Chunling
authors.initials: C
authors.lastname: Zhang
authors.forename: Haojie
authors.initials: H
authors.lastname: Shi
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Xiaomeng
authors.initials: X
authors.lastname: Wang
authors.forename: Beibei
authors.initials: B
authors.lastname: Lü
authors.forename: Shuping
authors.initials: S
authors.lastname: Zhang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Liang
authors.forename: Ruoxue
authors.initials: R
authors.lastname: Liu
authors.forename: Jun
authors.initials: J
authors.lastname: Qian
authors.forename: Weiwei
authors.initials: W
authors.lastname: Sun
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: You
authors.forename: Hansong
authors.initials: H
authors.lastname: Dong
mesh_terms: D000818:Animals; D001042:Aphids / Q000502:physiology*; D017360:Arabidopsis / Q000235:genetics* / Q000469:parasitology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D005247:Feeding Behavior; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D005966:Glucuronidase; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity; D052585:Phloem / Q000235:genetics / Q000469:parasitology*; D018515:Plant Leaves / Q000235:genetics / Q000469:parasitology; D037121:Plant Lectins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D027861:Prunus / Q000469:parasitology*
chemical_list: D029681:Arabidopsis Proteins; D001425:Bacterial Outer Membrane Proteins; C552547:PP2-A1 protein, Arabidopsis; D037121:Plant Lectins; C075462:harpin protein, Erwinia amylovora; D005966:Glucuronidase