Abstracts (first author)

Talk 

No strain no gain: genetic investigation of adaptive phenotypic plasticity in teleost jaws

Author(s): Gunter HM, Fan S, Xiong F, Schneider RF, Franchini P, Fruciano C, Meyer A

Summary:

Through incorporating environmental signals into ontogenetic pathways, phenotypically plastic species can fine-tune their phenotypes to precisely match local environmental conditions. In spite of its importance in the generation of adaptive phenotypes, the molecular basis of phenotypic plasticity remains poorly characterised. We are establishing a new molecular model for phenotypic plasticity research: the East African cichlid fish, Astatoreochromis alluaudi, which has been the subject of morphological studies of plasticity for 50 years. In response to a hard diet, its Lower Pharyngeal Jaw (LPJ) develops a ‘molariform’ morphology, with molar-like teeth set in an enlarged, dense jaw, compared with the smaller, finer ‘papilliform’ morphology which represents the ground state for this species. We performed a common garden experiment where siblings were fed either whole snails (hard diet), or finely minced snails (soft diet) and analysed the resulting morphological and transcriptional phenotypes. Genome-wide transcriptome analysis was performed on the LPJs of molariform and papilliform morphs that resulted from the diet treatments, shedding light on the environmentally sensitive pathways that modulate LPJ morphology. Numerous genes of mechanically responsive pathways (such as fos and jun) were upregulated in the molariform LPJs, indicating that mechanical strain intersects with bone developmental pathways that shape the molariform morphology. Intriguingly we also observe the down-regulation of various inflammatory factors and redox pathway members, suggesting that microenvironmental changes within the LPJ medullary cavity may alter cellular differentiation and proliferation. Through identifying numerous pathways involved with plasticity in the LPJ of A. alluaudi, our research opens the door to assess the role of phenotypic plasticity in generating morphological novelties amongst the explosive radiation of East African cichlid fishes.



Abstracts (coauthor)

Summary:

Heterochronic shifts in growth can generate novel, adaptive phenotypes that facilitate access to previously unoccupied niches. As they can arise from simple developmental switches, encoded by few mutations, novelties that arise through heterochronic shifts, are ideal systems for investigating the molecular basis of evolutionary change. Fishes from the suborder Belonioidei achieved a vast array of craniofacial morphologies that appear to have arisen through a series of heterochronic shifts. In some species (needlefishes) both the upper and lower jaws are highly elongated in others only the lower jaw (half-beaks). We examined the molecular basis of accelerated heterochronic growth in the lower jaw, relative to the upper jaw in the half beak Dermogenys pusilla, and compared it to a their sister group of the suborder the medaka, where this trait is ancestral, i.e., both jaws are equally long. Previous investigations have identified Calmodulin as a likely molecular determinant of accelerated jaw growth in D. pusilla, as its developmental expression reflects the relative growth of the jaws, while expression remains equal between the upper and lower jaws in medaka. Here we describe new transcriptome-wide analyses identify further candidates for accelerated jaw growth in the halfbeak, which also shed light on the structural composition of the tissues that comprise this morphological novelty. Furthermore, comparative gene expression analyses in medaka provide insights into the ancestral condition, enabling further assessments of mutational changes that may underlie a major heterochronic shift that is shared amongst the Belonoidei. As this shift appears to have been critical enabling the Belonoidei to occupy a greater number of trophic niches than the medaka, we postulate that this heterochronic shift explain the considerably greater evolutionary success of the Belonoidei compared to the medaka lineage.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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