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    Home > Food News > Food Articles > Scientists reveal the secret of Welwitschia "never fall leaves"

    Scientists reveal the secret of Welwitschia "never fall leaves"

    • Last Update: 2021-07-31
    • Source: Internet
    • Author: User
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    Scientists reveal the secret of Welwitschia "never fall leaves"
    Scientist research reveals the secret of Welwitschia "Never Falling Leaves" Scientist research reveals the secret of Welwitschia "Never Falling Leaves"

    Welwitschia
    .


    Photo by Wang Qingfeng

    Welwitschia


    Welwitschia, also known as Welwitschia, is a relict plant of the Centennial Orchidaceae, a single species of the cane
    .


    It has only two leaves in its lifetime, and it continues to grow without falling off.


    It is understood that since 2017, under the organization of the China-Africa Joint Research Center of the Chinese Academy of Sciences , the team of researcher Wang Qingfeng of the Wuhan Botanical Garden of the Chinese Academy of Sciences , the team of researcher Wan Tao of the Fairy Lake Botanical Garden of the Chinese Academy of Sciences in Shenzhen , as well as the Gobabeb Research Center of Namibia, the Kew Botanical Garden in the United Kingdom, and China Scientists from the Institute of Botany of the Academy of Sciences, Queen Mary University of London in England, University of Ghent in Belgium and other cooperative units jointly initiated the research work on the Welwitschia genome and adaptive evolution mechanism
    .

    Chinese Academy of Sciences

    After 3 consecutive years of field observation and sampling, the researchers used third-generation sequencing technology and Hi-C technology to assist assembly annotation to obtain the full-length genome sequence of Welwitschia 6.
    8G, Scaffold N50 reached 295.
    50 Mbp, 93.
    65% The sequence was anchored to 21 chromosomes, combined with RNA-seq, Bisulphite-seq, sRNA-seq, nuclear magnetic resonance, hormone determination and other analysis, the evolution history and ecological adaptability of Welwitschia were studied
    .

    The study found that an independent whole-genome doubling (WGD) occurred about 86 million years after the species differentiation of Welwitschia species.
    The genome experienced a violent transposon outbreak in the past 1 to 2 million years.
    Frequent non-homologous recombination cancels out most of the amplified transposon sequences
    .


    The time of the above changes has a strong correlation with the formation history of the Namib Desert (the oldest desert on the earth formed at least 80 million years ago) where the Welwitschia is located


    Through the methylation sequencing and comparison of the original meristems of Welwitschia and the old and new leaf segments, we found that the whole genome of Welwitschia was extremely heavily methylated, and the silencing was specifically regulated by the dynamic differences in methylation at CHH sites.
    Transposons to maintain the integrity of the meristem cell genome and avoid harmful mutations in DNA
    .


    Interestingly, severe methylation seems to accelerate the rate of deamination of the Welwitschia genome, making its GC content abnormally low


    Through comparative analysis with other representative land plants, related resistance genes (HSP, LRR, WRKY, bHLH, etc.
    ) have been significantly amplified in Welwitschia, involving many transcriptions of cell homeostasis, cell growth rate, and DNA repair The expression of factors, especially the co-expression mode of ARP and KNOX1, which regulates the meristems of plant meristems, is significantly different from other seed plants, which enables Welwitschia to continuously obtain newly differentiated leaf cells and ensure the continuity of the two leaves.
    Stretch
    .


    The study also found that the differential expression of the rate-limiting enzyme NCED4 for the synthesis of abscisic acid ABA in different tissues of Welwitschia may be caused by the regulation of CHH differential methylation in the promoter region


    The study showed that the genome evolution of Welwitschia has a strong correlation with the drastic changes in the geological environment and the effects of continuous high temperature and drought experienced in the past 100 million years, and it tends to be small and "low energy consumption"
    .


    Severe methylation and CHH site regulation effectively ensure the integrity of the Welwitschia genome during the generational alternation process; the changes in the expression patterns of transcription factors that regulate the development of primary meristems are likely to affect the current morphological pattern of this species.


    Related paper information: https://doi.


    https://doi.
    org/10.
    1038/s41467-021-24528-4 https://doi.
    org/10.
    1038/s41467-021-24528-4 https://doi.
    org/10.
    1038/s41467-021-24528- 4
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