Using Neurospora to demonstrate the unidirectional nature of fungal mating.
Kevin McCluskey
School of Biological Sciences, University of Missouri, Kansas City
Fungal Genetics Newsletter 52:9-10
Different fungi have been used to demonstrate mating in fungi including
Neurospora (Griffiths, 1979), Aspergillus (Denison, 2000), and Sordaria (Fields,
1970) and kits for demonstrating mating in Sordaria are available from Carolina
Biological, Inc. The present demonstration allows students to see both that
fungi have different mating types and that one strain acts as the female parent.
It takes advantage of the rapidity of Neurospora growth and the ease of using
fluffy strains (Table 1). Strains carrying the fluffy lesion are mated with fl
per-1 strains and the pattern of perethecial color on the resulting plates shows
which strain was the female parent.
Table 1. Strains used in the present study
| FGSC number |
Genotype |
Mating type |
| FGSC 4347 |
fl |
a |
| FGSC 4317 | fl |
A |
| FGSC 3311 | fl; per-1 |
A |
| FGSC 3312 | fl; per-1 |
a |
Matings were carried out on cornmeal agar (Difco #238620) using mycelia also
grown on cornmeal agar. The inoculum was cut from the starter plate using
sterilized drinking straws or a cork-borer. This allows for a very uniform
inoculum which contributes to the even and predictable nature of the resulting
cross plates. Agar plugs can be transferred to the mating plates using
sterilized toothpicks or with inoculating loops.
Plates were incubated at 22 - 24 C and rapid growth was observed after overnight
incubation. After five or six days perithecia were visible as a line separating
the original colonies (Figure 1).
The production of white perithecia, where the per-1 parent acts as the female
parent, is shown in Figure 1.A. The double line of perithecia, as described in
Griffiths (1979) is clearly seen in Figure 1. A. where two strains are paired on
one plate. This double line is more difficult to discern where four strains are
inoculated on one plate (Figure 1.B).
The timing makes this a suitable exercise for students who meet once or twice
each week. The inoculum could be set during the first week and the results would
be visible by the second week. The plates do not change appreciably in the
subsequent weeks and as such give students time to record their results.
A
|
B |
Figure 1. Mating between fluffy and fluffy perithecial-1 strains. A) two-strain
cross. B) four strain cross.
It is conceivable that this system could be used to present ‘unknowns’ to
students, as described by Griffiths (1979), where matings are carried out to
determine which strains carry opposite mating types. Alternatively, one strain
could be given with known mating type and the student could be left to determine
both the mating type and the nature of the per-1 locus (wt vs mutant) on
additional strains. Additional loci could be included for student
identification, including female fertility (ff) or perithecial neck (pen-1).
References
Fields, W. G. (1970) An introduction to the genus Sordaria. Neurospora
Newsletter, 16:14-17
Griffiths, A. J. F. (1979) A Neurospora experiment for an introductory biology
course. Neurospora newsletter 26:12
Denison, S. H. (2000) Teaching Genetics with Aspergillus nidulans. Carolina Tips
64:9-10
The FGSC is supported by the US National Science Foundation, Grants
0235887 and 0603830
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