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We present integral field spectroscopy observations of two star-forming dwarfgalaxies in the Virgo cluster (VCC135 and VCC324) obtained with PMAS/PPak atthe Calar Alto 3.5 meter telescope. We derive metallicity maps using the N2empirical calibrator. The galaxies show positive gas metallicity gradients,contrarily to what is usually found in other dwarfs or in spiral galaxies. Wemeasure gradient slopes of 0.20 $\pm$ 0.06 and 0.15 $\pm$ 0.03 dex/$R_e$ forVCC135 and VCC324, respectively. Such a trend has been only observed in few,very isolated galaxies, or at higher redshifts ($z >$ 1). It is thought to beassociated with accretion of metal-poor gas from the intergalactic medium, amechanism that would be less likely to occur in a high-density environment likeVirgo. We combine emission line observations with deep optical images toinvestigate the origin of the peculiar metallicity gradient. The presence ofweak underlying substructures in both galaxies and the analysis ofmorphological diagnostics and of ionised gas kinematics suggest that the inflowof metal-poor gas to the central regions of the dwarfs may be related to arecent merging event with a gas-rich companion.

Inverted metallicity gradients in two Virgo cluster star-forming dwarf galaxies: evidence of recent merging?