Investigation
The floral transition marks the initiation of reproductive development and the timing of this developmental switch is essential to determine the production of fruits and seeds and, therefore, the reproductive success of plant species. For that reason, plants tune very precisely the time of flowering initiation in response to both endogenous and environmental factors. Using the model plant species Arabidopsis thaliana, and related Brassicaceae crop species, during the last five years we have investigated several molecular mechanisms involved in the control of flowering.
Chromatin-mediated regulation of flowering time
Chromatin remodeling processes play essential roles in the establishment and maintenance of gene expression patterns that drive plant developmental transitions. For that reason, one of our main interests is to analyse the involvement of epigenetic processes in the control of flowering time. In this context, we have functionally characterized two homologous plant specific proteins, EBS and SHL, which contain functional domains that specifically recognize histone posttranslational modifications. Both proteins interact with chromatin remodelling complexes to repress the initiation of flowering by directly repressing the expression of master genes that function as flowering switches.
Additionally, we have established a conceptual model for the reestablishment of epigenetic marks following DNA replication in plants. Using flowering time in Arabidopsis as experimental system we have revealed a role for the DNA polymerase ϵ ESD7 in the maintenance of repressor marks in the chromatin through the interaction with Polycomb Group (PcG) proteins, showing the involvement of this DNA polymerase in the transcriptional silencing of key flowering genes by participating in the recruitment of these repressor complexes of gene expression.
Our work in the last few years has also unveiled the involvement of the SWR1-mediated exchange of non-canonical histone variants such as H2A.Z in the control of flowering time. Our characterization of several subunits of the SWR1 complex has demonstrated that this complex is a central player in the repression of flowering. Some of the subunits of this complex are shared with NuA4, a histone acetyltransferase complex functionally related to SWR1, prompting us to explore the involvement of NuA4 in the regulation of the floral transition, one of our current research interests. Our observations show that several subunits of this acetyltransferase complex are also required for proper control of flowering time.
Involvement of selective protein degradation in flowering time regulation
Our characterization of Arabidopsis mutants with altered flowering time allowed us to reveal the participation of selective protein degradation in the regulation of the photoperiodic flowering response. We have shown that the E3 ubiquitin ligase HOS1/ESD6 is necessary to modulate the stability of proteins that play essential roles in the daylength perception and the control of flowering time in response to photoperiod. In addition, our data are indicative that photoreceptors are also involved in this response, confirming that integration of light signals with selective protein degradation machinery is central to the regulation of plant development and particularly the floral transition.
Flowering response to temperatura in Brassica crops
Nowadays agriculture faces the challenge of securing stable and sustainable crop production in a fluctuating environment. Crop yield depends on the adaptive response of key developmental traits to varying environmental conditions due to climate change. In this context, our laboratory is focused on understanding the mechanisms that mediate the flowering response to high ambient temperature of Brassica crops. We are currently analysing the influence of increased temperature in the flowering time of these crops and the epigenetic mechanisms that mediate this response in crop species such as B. napus, B. rapa and B. oleracea.
The research line of the Ramón y Cajal researcher Pedro Crevillén is described in his web page.
