Meeting Abstract

25.5  Wednesday, Jan. 4  Genomic dynamics in a growing filamentous fungus ROPER, M.L.*; SIMONIN, A.; LEEDER, A.; GLASS, N.L.; UCLA; UC Berkeley; UC Berkeley; UC Berkeley

The syncytial cells of filamentous fungi may harbor tens, thousands or even millions of genetically diverse nuclei within a single shared cytoplasm. This genetic diversity is acquired by mutations when nuclei divide, or by fusion of neighboring fungi, followed by the exchange of genetic material. Increasing evidence shows that this internal genetic flexibility enhances virulence and the ability of fungi to utilize nutritionally complex substrates like plant cell walls, and is a motor for fungal diversification. However, maintaining genetic diversity during growth poses a difficult biophysical problem, since mycelia grow by the extension of hyphal tips, and this process naturally segregates out different nucleotypes. Using strains of the ascomycete species Neurospora crassa in which nucleotypes can be distinguished by fluorescently labeled histone proteins, I'll show that genetic diversity can be maintained at every length scale of the fungus at the cost of continuous physical mixing of nuclei and nucleotypes during growth. Remarkably these complex multidirectional mixing flows are apparently optimized for mixing, but yet must be realized by static and spatially coarse pressure gradient from the interior of the mycelium to the tips. The architecture beneath the apparently random branching of fungal hypha may therefore provide lessons for the design of efficient microfluidic reactors.