Src1 is essential.

<p>(A) Conidia (asexual spores) from wildtype control (<i>pyrG</i>⁺) <i>or</i> Δ<i>src1</i>::<i>pyrG</i> deletion primary transformants were replica streaked onto nonselective (+UU) and selective (-UU) plates and grown for 40 hours for photography. Conidia that are not able to grow on–UU media are from primary Δ<i>src1</i>::<i>pyrG</i> / <i>src1 pyrG</i>89 heterokaryon transformants indicating <i>src1</i> to be essential. (B) Bright field image of the limited growth of conidia from <i>Δsrc1</i>::<i>pyrG</i> / <i>src1 pyrG</i>89 heterokaryons on selective media for 24 and 72 h. Scale bar 10 μm. (C) Diagnostic PCR using DNA isolated from a wild-type strain (Wt.), from a putative heterokaryon grown in +UU media (stops selection for <i>Δsrc1</i>), and from a putative heterokaryon growing in-UU selective media. The deletion allele carried in the heterokaryotic transformant is rapidly lost upon propagation without selection indicating the transformant is not a diploid but a heterokaryon. (D) The degree of growth of both wildtype and <i>Δsrc1</i> cells were compared at 12, 15, and 18 hours at 23.5°C by measuring the average length of germlings. (E) <i>Δsrc1</i> germlings fixed and stained with DAPI to reveal nuclear defects, including condensed DNA, odd numbers of nuclei (indicated by white arrowheads), and an unusual pattern of nuclear transport evidenced by only one nucleus being able to accumulate NLS-DsRed (indicated by arrow). Scale bar 5 μm.