The mechanism of ascus firing – Merging biophysical and mycological viewpoints

Publication date: October 2014 Source:Fungal Biology Reviews, Volume 28, Issues 2–3 Author(s): Frances Trail , Agnese Seminara The actively discharging ascus is the unique spore-bearing cell that is responsible to dispatch spores into the atmosphere. From a physical perspective, this type of ascus is a sophisticated pressure gun that reliably discharges the spores at an extremely high velocity, without breaking apart. We identify four essential steps in discharge of spores whose order and timing may vary across species. First, asci that fire are mature, so a cue must be present that prevents discharge of immature spores and signals maturity. Second, pressure within the ascus serves to propel the spores forward; therefore a mechanism should be present to pressurize the ascus. Third, in ostiolate fruiting bodies (e.g. perithecia), the ascus extends through an opening to fire spores into the air. The extension process is a relatively unique aspect of the ascus and must be structurally facilitated. Fourth, the ascus must open at its tip for spore release in a controlled rupture. Here we discuss each of these aspects in the context of understanding the process of ascus and fruiting body function. While there is great diversity among fungi, we focus on discharge in a few model species, and then discuss how this framework may vary in other fungi. Our goal is to tie the physiological and molecular studies of ascus function with concepts in engineering that dictate structure.
Source: Fungal Biology Reviews - Category: Biology Source Type: research