%0 Journal Article
%T Gene up-regulation in response to predator kairomones in the water flea, Daphnia pulex
%A Hitoshi Miyakawa
%A Maki Imai
%A Naoki Sugimoto
%A Yuki Ishikawa
%A Asano Ishikawa
%A Hidehiko Ishigaki
%A Yasukazu Okada
%A Satoshi Miyazaki
%A Shigeyuki Koshikawa
%A Richard Cornette
%A Toru Miura
%J BMC Developmental Biology
%D 2010
%I BioMed Central
%R 10.1186/1471-213x-10-45
%X Previous studies suggest that the timing of the sensitivity to kairomones in D. pulex can generally be divided into the embryonic and postembryonic developmental periods. We therefore examined which of the genes in the embryonic and first-instar juvenile stages exhibit different expression levels in the presence or absence of predator kairomones. Employing a candidate gene approach and identifying differentially-expressed genes revealed that the morphogenetic factors, Hox3, extradenticle and escargot, were up-regulated by kairomones in the postembryonic stage and may potentially be responsible for defense morph formation. In addition, the juvenile hormone pathway genes, JHAMT and Met, and the insulin signaling pathway genes, InR and IRS-1, were up-regulated in the first-instar stage. It is well known that these hormonal pathways are involved in physiological regulation following morphogenesis in many insect species. During the embryonic stage when morphotypes were determined, one of the novel genes identified by differential display was up-regulated, suggesting that this gene may be related to morphotype determination. Biological functions of the up-regulated genes are discussed in the context of defense morph formation.It is suggested that, following the reception of kairomone signals, the identified genes are involved in a series of defensive phenotypic alterations and the production of a defensive phenotype.The ability to modulate development in the presence of predators is referred as "inducible defense" or "predator-induced polyphenism" [1]. Of the examples reported to date, the freshwater microcrustacean genus Daphnia, commonly called the waterflea, is considered to be a model case for elucidating the ecological and developmental underpinnings of this process [2]. D. pulex produces structures referred to as neckteeth on its head, primarily in the earlier instars (first to third instar), in the presence of predatory phantom midges (Chaoborus larvae) (Figure 1A,
%U http://www.biomedcentral.com/1471-213X/10/45