Evolutionary insights from comparative transcriptome and transcriptome-wide coalescence analyses in Tetrastigma hemsleyanum

December 19th, 2018
By Gitzendanner, Matt

Wang, Y., W. Jiang, W. Ye, C. Fu, M. A. Gitzendanner, P. S. Soltis, D. E. Soltis, and Y. Qiu. 2018. Evolutionary insights from comparative transcriptome and transcriptome-wide coalescence analyses in Tetrastigma hemsleyanum. BMC Plant Biology 18:208. [View on publisher’s site]

Abstract

Background

Tetrastigma hemsleyanum is of great medicinal importance and used as a model system to address the evolutionary history of warm-temperate evergreen (WTE) forest biomes in East Asia over Neogene time scales. However, further studies on the neutral and adaptive divergence processes of T. hemsleyanum are currently impeded by a lack of genomic resources. In this study, we de novo assembled and annotated a reference transcriptome for two cpDNA lineages (Central-South-East vs. Southwest) of T. hemsleyanum. We further used comparative genomic and multilocus coalescent approaches to investigate the tempo and mode of lineage diversification in T. hemsleyanum.

Results

A total of 52,838 and 65,197 unigenes with an N50 of 1,667 and 1,841 bp for Central-South-East (CSE) and Southwest (SW) lineages, respectively, were recovered, and 6,692 putative orthologs were identified between the two lineages. Estimation of Ka/Ks ratios for these orthologs revealed that ten genes had Ka/Ks values significantly greater than 0.5 (P < 0.05), whereas 2,099 (Ka/Ks < 0.5, P < 0.05) were inferred to be under purifying selection. Based on three bioinformatic strategies, we identified a total of 1,018 single-copy nuclear genes (SCNGs) from the orthologs. We successfully designed eight nuclear gene primer pairs with high intraspecific variation (e.g. hT = 0.923, πT = 1.68×10-3), when surveyed across a subset of T. hemsleyanum individuals. Concordant with the previous cpDNA data, the haplotype networks constructed for most nuclear gene loci clearly identified the two lineages. A multilocus coalescence analysis suggested that the separation between the two lineages appears to have occurred during the mid-Pliocene. Despite their ancient divergence, both lineages experienced expansion at rather localized scales and have continued to exchange genes at a low rate.

Conclusions

This study demonstrated the utility of transcriptome sequencing as a basis for SCNG development in non-model species and the advantages of integrating multiple nuclear loci for phylogeographic and phylogenetic studies.

Categories: Publications


No Comments

No comments yet.

RSS feed for comments on this post.

Sorry, the comment form is closed at this time.