title: Gene expression profiles in Rana pirica tadpoles following exposure to a predation threat.
abstract: BACKGROUND
  Rana pirica tadpoles show morphological changes in response to a predation threat: larvae of the dragonfly Aeshna nigroflava induce heightened tail depth, whereas larval salamander Hynobius retardatus induce a bulgy morphology with heightened tail depth. Although both predators induce similar tail morphologies, it is possible that there are functional differences between these tail morphs.
  
  
  RESULTS
  Here, we performed a discriminant microarray analysis using Xenopus laevis genome arrays to compare tail tissues of control and predator-exposed tadpoles. We identified 9 genes showing large-scale changes in their expression profile: ELAV-like1, methyltransferase like 7A, dolichyl-phosphate mannosyltransferase, laminin subunit beta-1, gremlin 1, BCL6 corepressor-like 1, and three genes of unknown identity. A further 80 genes showed greater than 5 fold differences in expression after exposure to dragonfly larvae and 81 genes showed altered expression after exposure to larval salamanders. Predation-threat responsive genes were identified by selecting genes that reverted to control levels of expression following removal of the predator. Thirteen genes were induced specifically by dragonfly larvae, nine others were salamander-specific, and sixteen were induced by both. Functional analyses indicated that some of the genes induced by dragonfly larvae caused an increase in laminins necessary for cell adhesion in the extracellular matrix. The higher expression of gremlin 1 and HIF1a genes after exposure to dragonfly larvae indicated an in vivo hypoxic reaction, while down-regulation of syndecan-2 may indicate impairment of angiogenesis. Exposure to larval salamanders caused down-regulation of XCIRP-1, which is known to inhibit expression of adhesion molecules; the tadpoles showed reduced expression of cα(E)-catenin, small muscle protein, dystrophin, and myosin light chain genes.
  
  
  CONCLUSIONS
  The connective tissue of tadpoles exposed to larval salamanders may be looser. The differences in gene expression profiles induced by the two predators suggest that there are functional differences between the altered tail tissues of the two groups of tadpoles.
authors.affiliation: Department of Marine Science and Resources, Nihon University College of Bioresource Sciences, Kameino 1866, Fujisawa, 252-0880, Japan. mori.tsukasa@nihon-u.ac.jp.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Mori
authors.affiliation: Department of Liberal Art, Nihon University College of Bioresource Sciences, Kameino 1866, Fujisawa, 252-0880, Japan. yukio713@brs.nihon-u.ac.jp.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Yanagisawa
authors.affiliation: Department of Marine Science and Resources, Nihon University College of Bioresource Sciences, Kameino 1866, Fujisawa, 252-0880, Japan. youichirokitani@hotmail.co.jp.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Kitani
authors.affiliation: Department of Marine Science and Resources, Nihon University College of Bioresource Sciences, Kameino 1866, Fujisawa, 252-0880, Japan. nautilus@gaea.ocn.ne.jp.
authors.forename: Manabu
authors.initials: M
authors.lastname: Sugiyama
authors.affiliation: Teshio Experimental Forest, Field Science Center for Northern Biosphere, Hokkaido University, Horonobe, Hokkaido, 098-2943, Japan. kishida@fsc.hokudai.ac.jp.
authors.forename: Osamu
authors.initials: O
authors.lastname: Kishida
authors.affiliation: Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, 041-8611, Japan. kinya@fish.hokudai.ac.jp.
authors.forename: Kinya
authors.initials: K
authors.lastname: Nishimura
mesh_terms: D000818:Animals; D003238:Connective Tissue / Q000378:metabolism*; D020387:Food Chain; D007313:Insecta / Q000254:growth & development / Q000502:physiology; D007814:Larva / Q000378:metabolism*; D011898:Ranidae / Q000033:anatomy & histology* / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D013315:Stress, Psychological / Q000378:metabolism*; D013623:Tail / Q000033:anatomy & histology* / Q000502:physiology; D059467:Transcriptome; D014562:Caudata / Q000254:growth & development / Q000502:physiology