Fig 1.

Experimental design and translocation of δ¹⁵N in N. crassa colonies. (A) Diagram of plates used for stable isotope translocation experiments. The plates were 24 by 24 cm and filled with low-sucrose agar covered with a nylon membrane, with glass slides placed at one edge of the plate. An inoculum strip of minimal medium agar containing a strip of hyphae was placed on the edge of the glass slides. [¹⁵N]AIB was added to the inoculum strip either at the start of the experiment or after the colonies had grown 3 cm. The letters indicate the 1.67-cm regions from which the colony biomass was harvested. (B) The amounts of δ¹⁵N in regions A, B, and C of the WT, ΔPrm-1, and Δso colonies were determined when a [¹⁵N]AIB tracer was added to the inoculation strip at the time of colony inoculation. (C) The amounts of δ¹⁵N in regions A, B, and C of the wild-type, ΔPrm-1, and Δso colonies were determined when a [¹⁵N]AIB tracer was added to the inoculation strip after 3 cm of linear growth. Bars indicate the standard errors.