We present preliminary results of VLT spectroscopy follow-up of Planetary Nebulae (PNe) and HII regions in the dwarf Irregular galaxy NGC 3109. In total we have observed 15 PNe (of a total of 18) and about 50 HII: at least for 10 PNe and 10 HII regions the very faint [O III]4363 line is observed allowing to derive accurate abundances. The comparison of the abundances with several other galaxies in the Local Group helps to trace general trends: these dwarf galaxies have low initial metallicities, but also He and N are less enriched compared to what it is observed in our Galaxy, M 33 or in the Magellanic Clouds. As already suspected in the LMC and the SMC, but now also seen at lower metallicities the abundances of O and Ne seems to be affected by nucleosynthesis during the life of the PN progenitor.