Workshop Innovative Strategies in Plant Research
About us
We are a multidisciplinary team composed by cell and molecular biologists and biochemists. Besides the group leader, Vicente Rubio, the group includes a “Ramón y Cajal” senior researcher, a PhD student, and two technicians. The size of the group tends to be increased by international visiting researchers and master students. Our group is located at the Plant Molecular Genetics Department at the CNB-CSIC, Madrid, Spain.
During the last 10 years the group has focused in the characterization of new functions of the ubiquitination machinery in plants. In this topic, we have paid special attention to E3 ubiquitin ligases, such as CRL4-CDDD complexes, that act as hubs to integrate signals from different abiotic stresses and environmental stimuli in plants to trigger coherent adaptive and developmental responses. As an example, we have shown that DDA1, a substrate adaptor of CRL4-CDDD complexes, recognises abscisic acid (ABA) receptors, triggering their ubiquitination and proteasomal degradation (Irigoyen et al., The Plant Cell 2014). Therefore, CRL4-CDDD complexes act as repressors of ABA-mediated water stress responses under optimal growth conditions (figure 1).
Figure 1:CULLIN4-RING E3 ubiquitin ligases (CRL4) promote ubiquitination and degradation of PYR/PYL/RCAR ABA receptors to modulate ABA signalling in Arabidopsis.
Interestingly, our research, and that of others, indicates that CRL4-CDDD complexes act in close proximity to the chromatin, controlling the stability and function of a plethora of chromatin remodeling machineries (histone and DNA modifiers) and transcription regulators (transcription elongation factors, histone chaperones, RNA PolII, …). These molecular functions hold a physiological relevance as impaired CRL4-CDDD function (i.e. weak and null loss-of-function mutation of their components) severely compromise plant processes that depend on correct chromatin-associated functions (i.e. gametogenesis, embryogenesis, DNA-damage repair, cell cycle control, environmental responses, and fitness). Very importantly, some of these defects also occur in animal systems when CRL4-CDDD activity is defective ( figure 2).
Currently, our objectives include the identification and characterization of mechanisms, involving CRL4-CDDD, that control the accumulation of specific epigenetic marks over the plant genome in response to environmental changes, to regulate expression of specific set of genes that lead to plant adaptation to changing climate conditions. An example of a molecular pathway controlling epigenetic homeostasis in response to external stimuli (i.e. light conditions) recently discovered through a collaboration with the group of Drs. Fredy Barneche and Chris Bowler (IBENS, Paris) can be seen in Nassrallah et al., eLife 2018. In this type of approaches we take advantage of our expertise in molecular biology, genetics, protein biochemistry, affinity purification of complexes, and plant proteomics. However, our understanding of the far-reaching consequences of the CRL4-CDDD activity on nuclear architecture and chromatin remodeling processes at a larger scale is scarce. To fulfill this limitation, we aim to identify and characterise additional mechanisms by which CRL4-CDDD controls the accumulation of specific epigenetic marks across the plant genome in response to environmental changes, thereby regulating the expression of specific sets of genes that confer plants the ability to adapt to changing climate conditions.
Figure 2 :Schematic representation of the chromatin functions in which Arabidopsis CRL4-CDDD and DWD-containing proteins play a role (figure adapted from Fonseca and Rubio, Frontiers in Plant Science 2019)