Adaptive Evolution of the Eda Gene and Scales Loss in Schizothoracine Fishes in Response to Uplift of the Tibetan Plateau

Cunfang Zhang,Guogang Li,Yongtao Tang,Chao Tong,Chenguang Feng,Renyi Zhang,Sijia Liu,Arne Ludwig,Kai Zhao,Zuogang Peng

doi:10.3390/ijms19102953

Abstract

Schizothoracine is the predominant wild fish subfamily of the Tibetan plateau (TP). Their scales, pharyngeal teeth and barbels have gradually regressed with increasing altitude. Schizothoracine have been divided into three groups: primitive, specialized and highly specialized. Ectodysplasin-A (Eda) has been considered as a major gene that contributes to the development of skin appendages. The present study cloned the Eda genes of 51 Schizothoracine fish species which represent the three groups and five Barbinae species. Phylogenetic analyses indicated that Eda may have acted as the genetic trigger for scale loss in the Schizothoracine. Furthermore, 14 single nucleotide polymorphisms (SNPs) and two deletions (18 bp and 6 bp in size), were also detected in the Eda coding sequence of the highly specialized group compared to the primitive group. The same SNPs and two indels result in four non-synonymous and two G-X-Y and 1 XY motif indels, which possibly contribute to significant structure changes in the Eda gene. The domain including (G-X-Y)n motif in the Eda gene is relatively conserved amongst teleosts. Based on the above results, we hypothesize that the evolution of Eda gene might be associated with the scale loss in Schizothoracine fishes in response to the phased uplift of the TP.

Highlights

The uplift of the Tibetan plateau (TP) is a major historical episode associated with the Earth’s evolutionary history
The results showed that the two G-X-Y and one XY motif deletion were detected exclusively in HSG Schizothoracine fishes, and the two G-X-Y motif deletion was observed in G. dybowskii and Diptychus maculatus, and only the X or XY motif deletion was identified in the other teleost groups (Figure S1)
Schizothoracine fish are the main fish species distributed across the TP

Summary

Introduction

The uplift of the Tibetan plateau (TP) is a major historical episode associated with the Earth’s evolutionary history. Phylogenetic reconstruction of mtDNA (including Cyt-b, 16SrRNA, COI and ND4) and nuclear DNA RAG2 gene [22] or mitochondrial genomes [23] has grouped together the three groups of Schizothoracine fish He et al [16,19] have suggested that Schizothoracine fish originated from a single clade of Barbinae. Wang et al [22] and Yonezawa et al [23] suggested that Schizothoracine fish could be polyphyletic, with PG and SG+HSG possibly originating from two distinct clades of Barbinae These results supported the idea for three groups of Schizothoracine that follow phenotypic evidences, like the scale loss, and using molecular markers.

Objectives

Methods

Results

Conclusion