  We present results of NTT spectroscopy of the one known planetary nebula (PN)
in the dwarf spheroidal galaxy Fornax, a gas-deficient Local Group galaxy that
stopped its star formation activity a few hundred million years ago. We
detected the [OIII] 4363 line with a signal-to-noise ratio of ~22. For the
first time we detected the weak [SII] 6717,6731 lines (I(6717+6731) ~0.01
I(Hbeta)), determined the electron number density (Ne(SII) = 750 cm^-3), and
calculated O, N, Ne, Ar, S, Cl, Fe, He and C abundances. The abundance analysis
presented here is based on the direct calculation of the electron temperature
Te and yields an oxygen abundance of 12+log(O/H) = 8.28+/-0.02. The analysis of
the O, Ne, Ar and S abundances shows that the original ISM oxygen abundance was
0.27+/-0.10 dex lower and that third-dredge-up self-pollution in oxygen took
place. The blue spectrum shows weak Wolf-Rayet features, and the progenitor
star is classified as a weak emission-line star. Four of the five PNe in dwarf
spheroidal galaxies are now known to show WR wind features. Overall, the
metallicity of the progenitor of the PN fits in well with stellar spectroscopic
abundances derived in previous studies as well as with the stellar
age-metallicity relation of Fornax.
