Role of ubiquitin in the control of plant growth and stress tolerance

Plant Developmental Biology
Centro Nacional de Biotecnología CSIC (CNB)

Our group is focused in the characterization of Cullin4 Ring E3 ubiquitin Ligases (CRL4) that regulate developmental and stress responses in plants. In this context, we have identified DDA1, a new subunit of CRL4 complexes, which controls abscisic acid (ABA) perception and signaling. Thus, we found that DDA1, as part of CRL4, interacts with ABA receptors of the PYR/PYL family and triggers their ubiquitination and degradation. Therefore, DDA1-containing CRL4 complexes act as repressors of ABA-mediated stress responses, including drought, extreme temperatures and osmotic stresses (Irigoyen et al., 2014. The Plant Cell). Thus, DDA1 levels can be manipulated in plants to modulate ABA perception, and therefore responses, leading to increased tolerance to harmful environmental conditions. On the contrary, increased DDA1 function leads to ABA desensibilization, which should increase plant development and crop yield under suboptimal growth conditions that do not compromise plant survival. Currently, we are using this technology to obtain multi-stress tolerant rice (in collaboration with chinese groups). Our major goals are.

-To characterize the molecular mechanism by which ABA controls the activity of DDA1-containing CRL4 ligases. Our data show that ABA increases the disassembly of such complexes, triggering their inactivation. Such a mechanism of E3 ligase inhibition by a hormone has not been reported so far. This process does not require de novo synthesis of proteins, so all factors required are likely present in ABA-responsive cells. Our objective is to find these factors and characterize their function towards CRL4 inactivation.

-To determine how a single E3 ubiquitin ligase enables interplay between distinct signaling pathways. Interestingly, we have found by protein complex purification using TAP technology, that substrate adaptors involved in photomorphogenesis or ABA signaling can coexist in the same CRL4 E3 ligase complex, which provides a crosstalk platform for both developmental and stress signaling pathways. Very importantly, we found these complexes can associate with chromatin and epigenetic machineries, which may help to directly transduce environmental and intracellular signals into changes in gene expression.

-To deepen into the applied aspects of our research.  Thus, we are currently generating tools to manipulate the expression and activity of CRL4 E3 ligases in order to improve water stress tolerance in crops. We have already begun by obtaining transgenic rice lines with enhanced DDA1 activity. Testing their performance and yield under suboptimal growth conditions, at the green house and in field trials, is ongoing.

Students interested in the offer will actively participate in these projects, which will provide them knowledge in plant developmental programs in response to environmental stimuli and stress conditions. For this, students will learn techniques from different areas, such as molecular biology, cell biology, protein biochemistry and proteomics, as well as plant biotechnology.

Biomolecules & Cell D.
Sandra Fonseca