title: Hessian fly larval feeding triggers enhanced polyamine levels in susceptible but not resistant wheat.
abstract: BACKGROUND
  Hessian fly (Mayetiola destructor), a member of the gall midge family, is one of the most destructive pests of wheat (Triticum aestivum) worldwide. Probing of wheat plants by the larvae results in either an incompatible (avirulent larvae, resistant plant) or a compatible (virulent larvae, susceptible plant) interaction. Virulent larvae induce the formation of a nutritive tissue, resembling the inside surface of a gall, in susceptible wheat. These nutritive cells are a rich source of proteins and sugars that sustain the developing virulent Hessian fly larvae. In addition, on susceptible wheat, larvae trigger a significant increase in levels of amino acids including proline and glutamic acid, which are precursors for the biosynthesis of ornithine and arginine that in turn enter the pathway for polyamine biosynthesis.
  
  
  RESULTS
  Following Hessian fly larval attack, transcript abundance in susceptible wheat increased for several genes involved in polyamine biosynthesis, leading to higher levels of the free polyamines, putrescine, spermidine and spermine. A concurrent increase in polyamine levels occurred in the virulent larvae despite a decrease in abundance of Mdes-odc (ornithine decarboxylase) transcript encoding a key enzyme in insect putrescine biosynthesis. In contrast, resistant wheat and avirulent Hessian fly larvae did not exhibit significant changes in transcript abundance of genes involved in polyamine biosynthesis or in free polyamine levels.
  
  
  CONCLUSIONS
  The major findings from this study are: (i) although polyamines contribute to defense in some plant-pathogen interactions, their production is induced in susceptible wheat during interactions with Hessian fly larvae without contributing to defense, and (ii) due to low abundance of transcripts encoding the rate-limiting ornithine decarboxylase enzyme in the larval polyamine pathway the source of polyamines found in virulent larvae is plausibly wheat-derived. The activation of the host polyamine biosynthesis pathway during compatible wheat-Hessian fly interactions is consistent with a model wherein the virulent larvae usurp the polyamine biosynthesis machinery of the susceptible plant to acquire nutrients required for their own growth and development.
authors.affiliation: Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA. shubha@purdue.edu.
authors.forename: Subhashree
authors.initials: S
authors.lastname: Subramanyam
authors.affiliation: Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA. nsardesai@dow.com.|Present address: Dow AgroSciences LLC, Indianapolis, IN, 46268, USA. nsardesai@dow.com.
authors.forename: Nagesh
authors.initials: N
authors.lastname: Sardesai
authors.affiliation: Department of Biological Sciences, University of New Hampshire, Durham, NH, 03824, USA. Subhash.Minocha@unh.edu.
authors.forename: Subhash C
authors.initials: SC
authors.lastname: Minocha
authors.affiliation: Department of Statistics, Purdue University, West Lafayette, IN, 47907, USA. zhengcheng@gmail.com.|Present address: Novartis Pharmaceuticals Corporation, East Hanover, NJ, 07936, USA. zhengcheng@gmail.com.
authors.forename: Cheng
authors.initials: C
authors.lastname: Zheng
authors.affiliation: Department of Entomology, Purdue University, West Lafayette, IN, 47907, USA. shukle@purdue.edu.|USDA-ARS Crop Production and Pest Control Research Unit, West Lafayette, IN, 47907, USA. shukle@purdue.edu.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Shukle
authors.affiliation: Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA. christie.williams@ars.usda.gov.|USDA-ARS Crop Production and Pest Control Research Unit, West Lafayette, IN, 47907, USA. christie.williams@ars.usda.gov.
authors.forename: Christie E
authors.initials: CE
authors.lastname: Williams
mesh_terms: D012437:Adenosylmethionine Decarboxylase / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D053898:Biosynthetic Pathways / Q000235:genetics; D004175:Diptera / Q000502:physiology*; D000518:Eflornithine / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D060434:Herbivory; D007814:Larva / Q000254:growth & development; D008954:Models, Biological; D009952:Ornithine / Q000378:metabolism; D009955:Ornithine Decarboxylase / Q000378:metabolism; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics / Q000469:parasitology; D011073:Polyamines / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014908:Triticum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000469:parasitology*; D014774:Virulence
chemical_list: D000596:Amino Acids; D011073:Polyamines; D012333:RNA, Messenger; D009952:Ornithine; D009955:Ornithine Decarboxylase; D012437:Adenosylmethionine Decarboxylase; D000518:Eflornithine