Many fungal species grow through a process of vesicle secretion that can be applied in a biotechnology setting to make commercial or medical products. However, the details of this process are unclear. Researchers in Japan used a high-speed imaging technique to visualize hyphal growth in the fungus Aspergillus nidulans. Several new features were uncovered, including the discovery that different vesicle types move at different velocities.
Most fungi grow through the extension of hyphae, which are fiber-like structures made of one or more cells encased within a single, long cell wall. The growing tip of a hypha is loaded with ChsB, a cell wall synthesis enzyme that helps to lengthen the cell wall. ChsB is carried through the hypha by small cellular sacs called vesicles. In order for hyphae to grow, the transport and release of ChsB by these vesicles needs to be precisely timed-and exactly how this timing is achieved is unclear.
To address these shortcomings, the researchers used a technique called high-speed pulse-chase imaging, which allowed them to follow ChsB by fusing it to a marker emitting red fluorescent light. After bleaching away background red light using a laser beam, a separate beam was aimed at a single spot in the hypha, causing ChsB to fluoresce. The team was then able to trace the movement of the fluorescent ChsB as vesicles carried it around the hypha.
The technique resulted in minimal background and allowed images to be taken, on average, every 50 milliseconds-a level of precision not previously seen in hyphae. Correspondingly, the study yielded many new insights into the timing of vesicle movement during fungal growth.
Posted by Dr. Tim Sandle