auxin is a central hormone that exerts pleiotropic effects on plant growth including the development of roots shoots flowers and fruit the perception and signaling of the plant hormone auxin rely on the cooperative action of several components among which auxin indole 3 acetic acid aux iaa proteins play a pivotal role in this study we identified and comprehensively analyzed the entire aux iaa gene family in tomato solanum lycopersicum a reference species for solanaceae plants and the model plant for fleshy fruit development functional characterization using a dedicated single cell system revealed that tomato aux iaa proteins function as active repressors of auxin dependent gene transcription with however different aux iaa members displaying varying levels of repression phylogenetic analysis indicated that the aux iaa gene family is slightly contracted in tomato compared with arabidopsis with a lower representation of non canonical proteins sl iaa genes display distinctive expression pattern in different tomato organs and tissues and some of them display differential responses to auxin and ethylene suggesting that aux iaas may play a role in linking both hormone signaling pathways the data presented here shed more light on sl iaa genes and provides new leads towards the elucidation of their function during plant development and in mediating hormone cross talk.