The story of the origin of the yew, what is the anticancer substance of the yew and how to breed and cultivate it?

Taxus is a relic plant, which means remnant, which refers to creatures that have existed since ancient times, but there are still remaining populations today. The fossil record of the yew can be extrapolated to the Jurassic period 200 million years ago, which was distributed in Eurasia at the same time as dinosaurs.

The island was formed 5 million years ago, and during the ice age about 1.1 million years ago, China's southern yew (Taxus mairei) moved south from the icy mainland to warmer Taiwan by seed transmission. At that time, due to the drop in sea level during the Ice Age, Taiwan was connected to the mainland, so it was possible to take refuge in Taiwan. But when the earth warms up, glaciers melt and sea levels rise, the yew that takes refuge in Taiwan settles in the high mountains of Taiwan and begins to differentiate. It still belongs to the same species as the southern yew in China, but the DNA is slightly different.

The yew growing in Taiwan was first called Taxus mairei. Later in Taiwan Flora, the yew distributed from Nanyang Peninsula to South China, Taiwan and the Philippines was called Taxus mairei (T. Sumatra). Then taxonomists named this species as Xizang yew (T. Taxus chinensis var. mairei, whose scientific name is T. Gorgeous yew. However, recent studies from chloroplast DNA and nuclear DNA show that it should be based on the scientific name of Taxus mairei (T. Taxus mairei is more correct.

Paclitaxel was first found in the bark of Taxus mairei in the United States and was approved for the treatment of ovarian cancer in 1992. Paclitaxel combines with human albumin to form a new anticancer drug, which can make paclitaxel enter the tumor more easily and can treat metastatic breast cancer, non-small cell lung adenocarcinoma and metastatic pancreatic cancer. The new drug synthesized by 10-DAB in 2010 was also approved by ​​ for the treatment of metastatic prostate cancer. The demand for paclitaxel raw materials is increasing, and the global demand is estimated to be about 3000 kg. Taiwan's biotech industry is not absent in the production of anticancer APIs. Pacific paclitaxel and docetaxel made in Taiwan account for 21% and 38% of the world's APIs, respectively, but all raw materials are imported.

Breeding and cultivation

Can Taxus mairei be used as a source of taxol or 10-DAB? In 1993, natural mother trees of Taxus mairei scattered in high mountains were collected and preserved by means of asexual propagation such as cutting, grafting, tissue culture and so on. It is estimated that the age of these natural mother trees has reached hundreds to thousands of years, and the seedlings propagated asexually retain the physiological age of the original mother trees and grow slowly. However, through continuous grafting on seed seedlings and tissue culture, these seedlings can be rejuvenated and young again.

In addition, seeds were collected from various mountainous areas of Taiwan to cultivate seed seedlings, and 10 dominant seedlings with good growth were selected to establish cultivation areas with original mother tree clones in Wulai, Nantou, Kaohsiung and Taitong. the growth of these varieties and the stability of paclitaxel content were monitored for a long time, and three strains were selected, named Yew Taihong No. 1 No. 2 and No. 3 respectively. These three varieties have established ear-picking orchards, which can produce tens of thousands of cuttings every year and propagate a large number of cuttings. one. Cuttings with a height of about 25 centimeters in five years can be planted on a farm to be cultivated in a tea garden. Three years later, the height of the seedlings is about 1 meter, and the branches with a height of more than 50 centimeters are harvested by a tea picker.

At present, Taihong 1 has the largest cultivation area and produces twice as much taxol as Taxus mairei, so it has established an industry to produce taxol by cultivating Taxus mairei in Taiwan. Due to the limitation of the cultivated area in the mountains of Taiwan, it is impossible to cultivate a large area like the medium-sized continental countries in Europe, America and India. At the same time, in response to the increasingly frequent extreme weather in Taiwan, such as typhoons, torrential rains, and droughts, the mixed agroforestry system is developed, that is, the yew is cultivated under the forest. After 10 years of cultivation, after more than 10 typhoons, including 88 floods, abnormal drought, branches and leaves and paclitaxel can maintain stable production.