title: Functional analysis of the Theobroma cacao NPR1 gene in Arabidopsis.
abstract: BACKGROUND
  The Arabidopsis thaliana NPR1 gene encodes a transcription coactivator (NPR1) that plays a major role in the mechanisms regulating plant defense response. After pathogen infection and in response to salicylic acid (SA) accumulation, NPR1 translocates from the cytoplasm into the nucleus where it interacts with other transcription factors resulting in increased expression of over 2000 plant defense genes contributing to a pathogen resistance response.
  
  
  RESULTS
  A putative Theobroma cacao NPR1 cDNA was isolated by RT-PCR using degenerate primers based on homologous sequences from Brassica, Arabidopsis and Carica papaya. The cDNA was used to isolate a genomic clone from Theobroma cacao containing a putative TcNPR1 gene. DNA sequencing revealed the presence of a 4.5 kb coding region containing three introns and encoding a polypeptide of 591 amino acids. The predicted TcNPR1 protein shares 55% identity and 78% similarity to Arabidopsis NPR1, and contains each of the highly conserved functional domains indicative of this class of transcription factors (BTB/POZ and ankyrin repeat protein-protein interaction domains and a nuclear localization sequence (NLS)). To functionally define the TcNPR1 gene, we transferred TcNPR1 into an Arabidopsis npr1 mutant that is highly susceptible to infection by the plant pathogen Pseudomonas syringae pv. tomato DC3000. Driven by the constitutive CaMV35S promoter, the cacao TcNPR1 gene partially complemented the npr1 mutation in transgenic Arabidopsis plants, resulting in 100 fold less bacterial growth in a leaf infection assay. Upon induction with SA, TcNPR1 was shown to translocate into the nucleus of leaf and root cells in a manner identical to Arabidopsis NPR1. Cacao NPR1 was also capable of participating in SA-JA signaling crosstalk, as evidenced by the suppression of JA responsive gene expression in TcNPR1 overexpressing transgenic plants.
  
  
  CONCLUSIONS
  Our data indicate that the TcNPR1 is a functional ortholog of Arabidopsis NPR1, and is likely to play a major role in defense response in cacao. This fundamental knowledge can contribute to breeding of disease resistant cacao varieties through the application of molecular markers or the use of transgenic strategies.
authors.affiliation: Huck Institute of Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Zi
authors.initials: Z
authors.lastname: Shi
authors.forename: Siela N
authors.initials: SN
authors.lastname: Maximova
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.forename: Joseph
authors.initials: J
authors.lastname: Verica
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Guiltinan
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002099:Cacao / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003517:Cyclopentanes / Q000378:metabolism / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005816:Genetic Complementation Test; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007113:Immunity, Innate / Q000235:genetics; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009154:Mutation; D054883:Oxylipins / Q000378:metabolism / Q000494:pharmacology; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D044224:Pseudomonas syringae / Q000502:physiology; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020156:Salicylic Acid / Q000378:metabolism / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D003517:Cyclopentanes; C105496:NPR1 protein, Arabidopsis; D054883:Oxylipins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D049452:Green Fluorescent Proteins; C011006:jasmonic acid; D020156:Salicylic Acid