Plants have evolved complex strategies in making developmental decisions. One of these is floral initiation- the transition from the vegetative to the reproductive state. This critical switch needs to be perfectly timed in order to ensure reproductive success. One of the main transcription factors activating the florigen flowering locus T (FT) is called CONSTANS (CO). CO is targeted by microProteins miP1a and miP1b, which function by sequestering CO in a non-functional complex. Consequently, plants overexpressing the microProteins exhibit a significantly delayed transition to flowering, because of the lack of active CO. This study aims at identifying the mechanism by which these microProteins act by identifying factors involved in miP signaling. We describe the formation of a miP1a/b-CO complex together with the transcriptional corepressor TPL and the histone demethylase JMJ14. Taken together, our findings suggest that these interacting components are part of a larger repressor complex preventing premature floral transition.

Till date, all the miPs described in plants target transcription factors. The lack of diversity of protein target classes can be attributed to the lack of functional characterization of smaller proteins. Using a computational approach, we identified putative microProteins that could target a diverse variety of protein classes. Using a synthetic microProtein approach, we demonstrate that miPs can target a diverse variety of target proteins, which makes them of interest as potential biotechnological tools.