title: A small intergenic region drives exclusive tissue-specific expression of the adjacent genes in Arabidopsis thaliana.
abstract: BACKGROUND
  Transcription initiation by RNA polymerase II is unidirectional from most genes. In plants, divergent genes, defined as non-overlapping genes organized head-to-head, are highly represented in the Arabidopsis genome. Nevertheless, there is scarce evidence on functional analyses of these intergenic regions. The At5g06290 and At5g06280 loci are head-to-head oriented and encode a chloroplast-located 2-Cys peroxiredoxin B (2CPB) and a protein of unknown function (PUF), respectively. The 2-Cys peroxiredoxins are proteins involved in redox processes, they are part of the plant antioxidant defence and also act as chaperons. In this study, the transcriptional activity of a small intergenic region (351 bp) shared by At5g06290 and At5g06280 in Arabidopsis thaliana was characterized.
  
  
  RESULTS
  Activity of the intergenic region in both orientations was analyzed by driving the beta-glucuronidase (GUS) reporter gene during the development and growth of Arabidopsis plants under physiological and stressful conditions. Results have shown that this region drives expression either of 2cpb or puf in photosynthetic or vascular tissues, respectively. GUS expression driven by the promoter in 2cpb orientation was enhanced by heat stress. On the other hand, the promoter in both orientations has shown similar down-regulation of GUS expression under low temperatures and other stress conditions such as mannitol, oxidative stress, or fungal elicitor.
  
  
  CONCLUSIONS
  The results from this study account for the first evidence of an intergenic region that, in opposite orientation, directs GUS expression in different spatially-localized Arabidopsis tissues in a mutually exclusive manner. Additionally, this is the first demonstration of a small intergenic region that drives expression of a gene whose product is involved in the chloroplast antioxidant defence such as 2cpb. Furthermore, these results contribute to show that 2cpb is related to the heat stress defensive system in leaves and roots of Arabidopsis thaliana.
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina. bondino@ibr.gov.ar
authors.forename: Hernán G
authors.initials: HG
authors.lastname: Bondino
authors.forename: Estela M
authors.initials: EM
authors.lastname: Valle
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D003080:Cold Temperature; D021901:DNA, Intergenic / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005966:Glucuronidase / Q000378:metabolism; D006358:Hot Temperature; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000235:genetics*; D054464:Peroxiredoxins / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D013312:Stress, Physiological / Q000235:genetics
chemical_list: D020121:5' Untranslated Regions; D029681:Arabidopsis Proteins; D021901:DNA, Intergenic; D054464:Peroxiredoxins; D005966:Glucuronidase