The Mediator Complex and its role in flowering time, circadian rhythm and reproduction in Arabidopsis thaliana

JASKOLOWSKI A; ARELLANO S.M; IÑIGO S; LICHY M.Z; CERDAN P.D

Buenos Aires

Simposio; II Simposio de Fronteras en Biociencia; 2016

In eukaryotes, coding genes are transcribed by the RNA Polymerase II, and this process is regulated by transcription factors. However, these do not act directly on the RNA Polymerase II, but instead they do it through the Mediator Complex. Biochemical and structural studies show that the Mediator Complex is composed by three modules: head, middle and tail, and a ?accessory? module that has regulatory functions, the CDK module. In general terms, the head and middle modules interact with the RNA Polymerase II and the general transcription factors (GTFs), on the other hand the tail module interacts with the specific transcription factors and transmit the signals to the basal transctiptional machinery through the head and middle modules. In Arabidopsis, there are 54 genes encoding subunits of the complex, and so far only 42% of them have been characterized in some aspect of its function. The Mediator Complex acts as an integrator of diverse environmental responses, though the mechanisms are unknown. To begin to study its role in different aspects of development, we selected T-DNA insertional lines for each subunit, and searched for homozygous. Nevertheless, for a small group this proved to be impossible, presumable because they?re non-viable. Hence, we analyzed the heterozygous plants segregation and performed reciprocal crosses to determine if the problem is at the embryo level or gamete. For those subunits where homozygous mutations were not achieved, we employed artificial microRNAs to suppress the subunit coding gene expression. In parallel, we performed flowering time assays to determine which subunits are important to control this process. We are currently working on three of them, that presumably control flowering time by a photoperiod independent pathway.