Compared with some trees that have grown vigorously for hundreds or even thousands of years in nature, the longevity of animals is nothing compared to the abundance of trees in nature. But it has been unclear about the longevity of trees, such as Ginkgo. Recently, the Proceedings of the National Academy of Sciences published online the most comprehensive tree longevity mechanism research results of the team of Chinese and foreign scientists. They chose ginkgo trunk formation layer as the main research material, and used cytology, physiology, multi-group science and molecular biology to reveal the internal mechanism of ginkgo tree longevity.
The millennium-old ginkgo trees in Lijiawan, Fuquan City, Guizhou Province, are still growing strongly. Tian Liang Supply Map
Wang Li, a professor at Yangzhou University and author of the paper, told the China Science Daily that tree growth mainly comes from the division of the top sub-tissue and lateral tube formation, but the trees do not rise after a certain age, and therefore cannot reflect age changes. Each year, the formation layer of the tree trunk tube can divide and divide the new ligament and wood parts, and maintain the growth of the tree body, which is the ideal material for studying the longevity mechanism of ancient trees.
The study, using the analysis of DBHs by annual wheel determination techniques, determined the true age of 34 Ginkgo trees, with age ranging from 15 to 1353 years, and divided the trees of different tree ages into three groups for comparative study. It was found that compared with adult trees, the formation of the ancient tree group (193-667) formed a smaller number of layer cells, the newly produced annual wheel width narrowed, the content of growth hormone (IAA) decreased, shedding acid (ABA) content increased, cell division and differentiation related gene expression decreased, indicating that the growth of the ancient tree’s maintenance tube tissue slowed. However, the cross-sectional area increase (BAI) of the ancient tree trunk is still at a high level, indicating that Ginkgo tree formation layer stem cells still have a strong continuous division ability.
The study further determined the photosynthesis index of ancient leaf flakes, seed reproduction ability, aging-related marker genes, miRNA and target genes, autophagy genes, etc., and found no significant changes. In addition, the researchers tested the genes in ginkgo leaf aging process and other Ginkgo plants of more age. The results at these morphological, physiological and molecular levels reveal that ginkgo trees are still in a healthy adult state as a whole, still maintain “youthful vitality” and have not yet entered the aging stage. “The continuous division of Ginkgo ancient tree tube-forming layer cells plays an important role in avoiding aging. Wang Li said.
The paper’s author, Lin Jinxing, a professor at Beijing Forestry University, said trees eventually age and die mostly because of environmental stress or disease. To see if trees are more susceptible to this stress as they age, they examined genes associated with pathogen resistance and the production of protective substances. As a result, they identified 62 FLS2, EFR members and 457 R genes, especially r genes, in Ginkgo ancient tree-forming layer cells. In addition, there was no decrease in the number and expression of the gene in the metabolic pathways of lignin monomers, flavonoids and ferns in the paleogroup group.
The paper’s author, Richard Dixon, a professor at the University of North Texas at Denton, said it was an “amazing” ability to help Ginkgo grow healthy for thousands of years. Ginkgo ancient trees may increase the density and strength of tree trunks by continuoussynthesis of substances such as lignin to support the thickening of the tree, while improving tree resistance and resisting various biological and non-biological stress by continuously synthesizing substances such as lignin to support the growing thickening of the tree, while increasing tree resistance through the continuous expression of a large number of R genes and the accumulation of metabolites with special protective functions.
In summary, scientists believe that Ginkgo ancient tree longevity is not a single longevity gene regulation, but the growth and aging process of a combination of factors. The results of this study are of great scientific significance to reveal the mechanism of tree growth and aging regulation at the individual level.
The work has been funded by projects such as the National Natural Science Foundation of China and the 111-year-largest project.
Related papers: https://doi.org/10.1073/pnas.1916548117