Abstract
Dalbergia is a pantropical genus with more than 250 species, many of which are highly threatened due to overexploitation for their rosewood timber, along with general deforestation. Many Dalbergia species have received international attention for conservation, but the lack of genomic resources for Dalbergia hinders evolutionary studies and conservation applications, which are important for adaptive management. This study produced the first reference transcriptomes for 6 Dalbergia species with different geographical origins and predicted ~ 32 to 49 K unique genes. We showed the utility of these transcriptomes by phylogenomic analyses with other Fabaceae species, estimating the divergence time of extant Dalbergia species to ~ 14.78 MYA. We detected over-representation in 13 Pfam terms including HSP, ALDH and ubiquitin families in Dalbergia. We also compared the gene families of geographically co-occurring D. cochinchinensis and D. oliveri and observed that more genes underwent positive selection and there were more diverged disease resistance proteins in the more widely distributed D. oliveri, consistent with reports that it occupies a wider ecological niche and has higher genetic diversity. We anticipate that the reference transcriptomes will facilitate future population genomics and gene-environment association studies on Dalbergia, as well as contributing to the genomic database where plants, particularly threatened ones, are currently underrepresented.
Highlights
Dalbergia is a pantropical genus with more than 250 species, many of which are highly threatened due to overexploitation for their rosewood timber, along with general deforestation
All Dalbergia species are listed in the Convention on International Trade in Endangered Species (CITES) Appendix II, albeit their seeds are exempted according to Annotation #15
Total RNA was successfully extracted from leaf, stem and root tissues of each of 6 Dalbergia species and the RNA integrity numbers (RIN) of the RNA pools were all above 7.0
Summary
Dalbergia is a pantropical genus with more than 250 species, many of which are highly threatened due to overexploitation for their rosewood timber, along with general deforestation. Many Dalbergia species produce valuable heartwood timber known as rosewood, and are incorporated in a wide range of uses including furniture, boats, and musical instruments[4]. They are often targeted in illegal harvesting and traded in local and global markets with little regulation either in Asia (including the Indochina biodiversity hotspot) or Africa ( in Madagascar)[5,6]. A number of DNA-based barcodes have been developed that may be used in conservation forensics to track illegal trade and verify species identification[11]
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