Characterisation of the Cinnamomum parthenoxylon (Jack) Meisn (Lauraceae) transcriptome using Illumina paired-end sequencing and EST-SSR markers development for population genetics

Abstract

Cinnamomum parthenoxylon is an endemic and endangered species with significant economic and ecological value in Vietnam. A better understanding of the genetic architecture of the species will be useful when planning management and conservation. We aimed to characterize the transcriptome of C. parthenoxylon, develop novel molecular markers, and assess the genetic variability of the species. First, transcriptome sequencing of five trees (C. parthenoxylon) based on root, leaf, and stem tissues was performed for functional annotation analysis and development of novel molecular markers. The transcriptomes of C. parthenoxylon were analyzed via an Illumina HiSeqTM 4000 sequencing system. A total of 27,363,199 bases were generated for C. parthenoxylon. De novo assembly indicated that a total of 160,435 unigenes were generated (average length = 548.954 bp). The 51,691 unigenes were compared against different databases, i.e. COG, GO, KEGG, KOG, Pfam, Swiss-Prot, and NR for functional annotation. Furthermore, a total of 12,849 EST-SSRs were identified. Of the 134 primer pairs, 54 were randomly selected for testing, with 15 successfully amplified across nine populations of C. parthenoxylon. We uncovered medium levels of genetic diversity (PIC = 0.52, Na = 3.29, Ne = 2.18, P = 94.07%, Ho = 0.56 and He = 0.47) within the studied populations. The molecular variance was 10% among populations and low genetic differentiation (Fst = 0.06) indicated low gene flow (Nm = 2.16). A reduction in the population size of C. parthenoxylon was detected using BOTTLENECK (VP population). The structure analysis suggested two optimal genetic clusters related to gene flow among the populations. Analysis of molecular variance (AMOVA) revealed higher genetic variation within populations (90%) than among populations (10%). The UPGMA approach and DAPC divided the nine populations into three main clusters. Our findings revealed a significant fraction of the transcriptome sequences and these newlydeveloped novel EST-SSR markers are a very efficient tool for germplasm evaluation, genetic diversity and molecular marker-assisted selection in C. parthenoxylon. This study provides comprehensive genetic resources for the breeding and conservation of different varieties of C. parthenoxylon.

Keywords

• endangered species
• genetic diversity
• genetic str