Researchers have identified a "turning point" in the evolution of fungi, where growth inhibition occurs, shaping their morphology. Published in the journal Cell Reports, the findings suggest that minor changes in the environment can result in significant evolutionary outcomes.
The adaptive landscape of mycelium suggests that natural shapes are constrained by critical points.
Image Source: Maxim Oreshkin
Fungi are magnificent transformers of nature. They lie in wait on the forest floor, feasting on fallen trees and autumn leaves, returning essential nutrients back to the earth. Fungi also have underground roots, known as mycelium. Mycelium consists of tiny finger-like cells called hyphae, which interconnect by the thousands, growing into vast networks.
Hyphal Body
The shape of hyphae varies widely. To understand the reasons behind these differences, the research team first employed a physics-based model of tip growth to determine all possible shapes of hyphae. They then examined the growth rates of hyphae with different shapes to create an adaptive landscape of hyphae. This landscape, akin to a visual map of organismal evolution, indicates that a species only stops "exploring" evolutionarily when new mutations decrease its fitness (i.e., when it reaches a fitness peak).
The team discovered that the adaptive landscape of hyphae contains a "cliff" or critical point, which acts as an evolutionary barrier, severely constraining hyphal shapes. Consequently, they predicted that hyphae near the edge of this critical point are particularly susceptible to small environmental, chemical, or genetic changes.
Tests showed that one chemical could reduce the pressure within hyphae, while another chemical from sponges could inhibit the ability of hyphae to transport cellular components to the tip of the cell. Both treatments resulted in similarly significant effects: slower hyphal elongation and the formation of peculiar small shapes not found in nature.
The researchers believe that these findings are crucial for understanding many ecological and evolutionary systems. Moreover, by identifying growth vulnerabilities associated with the evolutionary critical point, this discovery could aid in developing novel antifungal drugs targeting pathogenic fungi.
