Highlights •The cancer drug Taxol is a fungicide against wood-decaying fungi (WDF) in yew trees •Inside yew, a fungal endophyte produces Taxol and migrates to pathogen entry points •The endophyte sequesters Taxol in hydrophobic bodies (HBs); WDF induce their release •The HBs can coalesce to form extracellular barriers laced with fungicidal Taxol
The researchers found naturally occurring fungi in the yew’s vascular system act like an immune system to swarm a wound site and protect against invading pathogens. Taxol is harvested from yew bark for use as an important cancer-fighting drug, but efforts to make synthetic taxol in the lab have been unsuccessful.
Raizada said the findings might point drug makers to a less expensive synthetic process for making more of the substance. Drug companies may harness beneficial fungi to pump out more taxol cheaply and easily to meet demand – a “holy grail” for cancer drug makers. Researchers have wondered why yew trees and non-pathogenic fungi living in them both produce taxol, a redundant process that uses a lot of energy and nutrients.
The answer lies in the unusual way yews and their relatives make new branches. Yews branch from buds under the bark. Branching causes cracks to open deep into the tree’s vascular system, an open wound that invites disease-causing fungi. Taxol normally helps protect against pathogenic fungi. But the substance is toxic to the tree’s own young buds.
The researchers found that naturally occurring fungi in the yew’s vascular system act like an immune system to swarm a wound site and protect against invading pathogens. The taxol fungicide is contained in “fatty bodies” that direct it only against pathogens and not the tree’s sensitive tissues.
“The fatty bodies come together to form a wall and seal the wound site,” says Raizada. “It’s really amazing, it’s so beautiful.” Yews are ancient trees related to ginkgo and Wallemi pine, with similar branch cracking and contain similar fungal species. Raizada now hopes to learn more about the genes and chemical pathways involved in making taxol in both trees and fungi. It might also help the agriculture and forestry sector. “They should be aware of these microbes because they might become organic bio-control agents.” http://news.uoguelph.ca/2015/09/fungi-may-lead-to-holy-grail-in-cancer-treatment-u-of-g-study/
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