Confronting climate change: the genetic makeover of a threatened conifer

A rare conifer, Cupressus gigantea, has an unexpectedly lower genetic load despite its dwindling population size. This study explores the evolutionary strategy behind its survival, focusing on the purging of deleterious mutations that contribute to its enduring legacy in the face of climate change and habitat fragmentation.

Conifers like Cupressus gigantea face significant threats from climate change and human activities, leading to habitat fragmentation and population decline. These challenges reduce genetic diversity and increase inbreeding, potentially accumulating harmful mutations. Previous studies have focused on the genetic impacts of population decline in various species, but little is known about such effects in conifers due to their large genomes. Based on these challenges, it is crucial to conduct in-depth research on the genetic burden and purifying selection in Cupressus species.

A team of researchers from Sichuan University and other institutions published a study (DOI: 10.1093/hr/uhae108) in Horticulture Research on 11 April 2024, uncovering the genetic resilience of the rare Tibetan cypress (Cupressus gigantea). This study, utilizing a newly assembled high-quality genome, reveals how prolonged inbreeding and historical climate events have influenced the genetic diversity and fitness of this endangered conifer. By comparing it with its widespread relative, Cupressus duclouxiana, the research provides valuable insights for the conservation of rare conifer species.

The study generated a 10.92 Gb high-quality genome for Cupressus gigantea and compared it with Cupressus duclouxiana using genomic data from 83 individuals. The results showed a significant reduction in the population size of C. gigantea during the early Quaternary, with no recovery until recently, unlike the recovering populations of C. duclouxiana. Despite having lower overall genomic diversity, C. gigantea exhibited fewer deleterious mutations, suggesting effective purifying selection during prolonged inbreeding. This genetic purging likely helped reduce the genetic burden, enhancing the species' survival despite its reduced population size. The study also highlighted that the genetic load of C. gigantea was lower than expected, with fewer loss-of-function and deleterious alleles in runs of homozygosity. These findings suggest that the endangered cypress has undergone genetic adaptations that could be crucial for its conservation. The genomic insights provided by this study emphasize the need for effective genetic management in conserving long-lived conifer species with large genomes, ensuring their survival in changing environmental conditions.

Dr. Kangshang Mao, one of the lead researchers, stated, "Our findings underscore the importance of genetic purging in the survival of endangered species like Cupressus gigantea. By understanding these genetic mechanisms, we can develop better conservation strategies to protect and manage these rare and valuable conifers."

The implications of this research extend beyond the survival of a single species. Understanding genetic purging could inform conservation strategies for other endangered species facing similar threats. Moreover, the insights into large genome management may contribute to broader ecological and environmental restoration efforts, ensuring the continued existence of these ancient conifers in a changing world.

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References

DOI

10.1093/hr/uhae108

Original Source URL

https://doi.org/10.1093/hr/uhae108

Funding information

This work was financially supported by the National Natural Science Foundation of China 536 (Grant/Award Number: U20A2080), the Second Tibetan Plateau Scientific Expedition and 537 Research (STEP) program (Grant/Award Number: 2019QZKK05020110), Sichuan Science and 538 Technology Program (Grant/Award Number: 2023NSFSC0186), Fundamental Research Funds for 539 the Central Universities of Sichuan University (Grant/Award Number: SCU2021D006 and 540 SCU2022D003) and Institutional Research Fund from Sichuan University (2021SCUNL102).

About Horticulture Research

Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2022. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.