Researchers identify double mechanism that regulates how plants react to drought

Researchers of the Institute of the Molecular and Cellular Biology of Plants (IBMCP), mixed centre of Valencia’s Polytechnic University (UPV) and the Spanish National Research Council (CSIC), have identified a double mechanism, of inhibition and degradation, to regulate the response of plants to drought. The results of this research, which increases available knowledge on how plants respond to environmental stress, have been published in the Proceedings of the National Academy of Sciences journal.
Plants must effectively respond to a broad variety of environmental stimuli. To do so, they have different signalling paths that are blocked by repressors as they wait for the appropriate stimulus. The removal of these repressors makes it possible to put into effect the signalling of several hormone paths, including the one that occurs when faced with drought, which is governed by abscisic acid (ABA). Pedro Luís Rodríguez, research professor of the CSIC at the IBMCP, explains that “until now, we knew that hormone ABA, after being perceived by its receptors, triggered the inhibition of the repressors of the answer to drought, which are the 2C phosphatase proteins. In this work, we have discovered a supplementary mechanism based on BPM proteins, which regulate the degradation of these repressors.”
Ubiquitin is a regulatory protein that is present in all eukaryote cells. One of its tasks is to guide the recycling of proteins. Ubiquitin can link to proteins and mark them to be destroyed through a complex process known as ubiquitination and requires proteins with E3 ubiquitin ligase activity. The ubiquitin’s mark guides proteins to the proteasome, which is a cellular machine that degrades and recycles proteins.
The IBMCP researchers have discovered that BPM proteins facilitate the ubiquitination of 2C-type phosphatases, which leads to their degradation in the proteasome. This process takes place in a regulated manner, as the hormone itself facilitates the degradation of the phosphatases.
“The BPM proteins recognise 2C-type phosphatases and facilitate their marking with ubiquitin, which leads to the degradation of these repressors. This makes it possible, for example, for the perspiration of the plant to decrease in a situation of drought, which represents a key adaptation. If the degradation of 2C-type phosphatases was accelerated, plants with better resistance to drought could be obtained,” adds Pedro Luís Rodríguez.
“In general, plants have a vast arsenal of proteins that degrade the repressors of their adaptive responses, so that the mechanism only triggers when necessary. In nature, plants suffer environmental stress in a transient or continued manner, and the existence of a double mechanism of inhibition and degradation to remove the hindrance of the adaptative answer provides greater versatility,” concludes Rodríguez.
Researchers from the CNRS (France) and the universities of Tartu (Estonia), Pekin (China) and California (USA) have also taken part in this work.