title: Expression profiling of marker genes responsive to the defence-associated phytohormones salicylic acid, jasmonic acid and ethylene in Brachypodium distachyon.
abstract: BACKGROUND
  Brachypodium distachyon is a promising model plants for grasses. Infections of Brachypodium by various pathogens that severely impair crop production have been reported, and the species accordingly provides an alternative platform for investigating molecular mechanisms of pathogen virulence and plant disease resistance. To date, we have a broad picture of plant immunity only in Arabidopsis and rice; therefore, Brachypodium may constitute a counterpart that displays the commonality and uniqueness of defence systems among plant species. Phytohormones play key roles in plant biotic stress responses, and hormone-responsive genes are used to qualitatively and quantitatively evaluate disease resistance responses during pathogen infection. For these purposes, defence-related phytohormone marker genes expressed at time points suitable for defence-response monitoring are needed. Information about their expression profiles over time as well as their response specificity is also helpful. However, useful marker genes are still rare in Brachypodium.
  
  
  RESULTS
  We selected 34 candidates for Brachypodium marker genes on the basis of protein-sequence similarity to known marker genes used in Arabidopsis and rice. Brachypodium plants were treated with the defence-related phytohormones salicylic acid, jasmonic acid and ethylene, and their transcription levels were measured 24 and 48 h after treatment. Two genes for salicylic acid, 7 for jasmonic acid and 2 for ethylene were significantly induced at either or both time points. We then focused on 11 genes encoding pathogenesis-related (PR) 1 protein and compared their expression patterns with those of Arabidopsis and rice. Phylogenetic analysis suggested that Brachypodium contains several PR1-family genes similar to rice genes. Our expression profiling revealed that regulation patterns of some PR1 genes as well as of markers identified for defence-related phytohormones are closely related to those in rice.
  
  
  CONCLUSIONS
  We propose that the Brachypodium immune hormone marker genes identified in this study will be useful to plant pathologists who use Brachypodium as a model pathosystem, because the timing of their transcriptional activation matches that of the disease resistance response. Our results using Brachypodium also suggest that monocots share a characteristic immune system, defined as the common defence system, that is different from that of dicots.
authors.affiliation: Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan. ykouzai@okayama-u.ac.jp.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kouzai
authors.affiliation: Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan. pmmc9ur9@okayama-u.ac.jp.
authors.forename: Mamiko
authors.initials: M
authors.lastname: Kimura
authors.affiliation: Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan. la_chatte_bleu_ciel@yahoo.co.jp.
authors.forename: Yurie
authors.initials: Y
authors.lastname: Yamanaka
authors.affiliation: Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan. po7l1am9@okayama-u.ac.jp.
authors.forename: Megumi
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan. hmatsui@okayama-u.ac.jp.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Matsui
authors.affiliation: Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan. myama@okayama-u.ac.jp.
authors.forename: Mikihiro
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan. yuki@okayama-u.ac.jp.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ichinose
authors.affiliation: Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan. pisatin@okayama-u.ac.jp.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Toyoda
authors.affiliation: Cellulose Production Research Team, Biomass Engineering Research Division, RIKEN Center for Sustainable Resource Science, Tsurumi, Yokohama, Japan. yoshihiko.onda@riken.jp.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Onda
authors.affiliation: Cellulose Production Research Team, Biomass Engineering Research Division, RIKEN Center for Sustainable Resource Science, Tsurumi, Yokohama, Japan. keiichi.mochida@riken.jp.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Mochida
authors.affiliation: Graduate School of Environmental and Life Science, Okayama University, Kita-ku, Okayama, Japan. noutoshi@okayama-u.ac.jp.
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Noutoshi
mesh_terms: D058431:Brachypodium / Q000235:genetics* / Q000276:immunology; D003517:Cyclopentanes / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism*; D020869:Gene Expression Profiling; D017343:Genes, Plant; D005819:Genetic Markers; D054883:Oxylipins / Q000378:metabolism*; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology; D010937:Plant Growth Regulators / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism*
chemical_list: D003517:Cyclopentanes; D005030:Ethylenes; D005819:Genetic Markers; D054883:Oxylipins; D010937:Plant Growth Regulators; D010940:Plant Proteins; C011006:jasmonic acid; C036216:ethylene; D020156:Salicylic Acid