Plant uses microRNA To to adapt to drought

Finding reveals that mechanism represents an evolutionary response to water stress situations

Plant uses microRNA To to adapt to drought

Finding reveals that mechanism represents an evolutionary response to water stress situations

Throughout evolution, living organisms, such as plants, develop strategies to deal with environmental adversities. In the case of water stress, caused by a period of drought, scientists discovered that a microRNA contributes to the model plant Arabidopsis thaliana have a better answer. The discovery was published in the journal plant physiology, with biologist João Vieira as the main author, whose doctorate in genetics and molecular biology, completed at the Center for Molecular Biology and Genetic Engineering (CBMEG) at Unicamp, focused on the subject. The finding contributes to understanding evolutionary processes when it comes to the strategies adopted by plants when faced with adverse conditions. 

A plant can suffer stress, explains Vieira, due to several environmental factors. In the case of water stress, the plant produces a hormone called abscisic acid (ABA). ABA binds to its receptors (proteins), known as PYL/PYR/RCAR, forming ABA-PYL complexes. These complexes activate proteins called kinases, which trigger the plant's adjustment responses to stress. The succession of these events constitutes the ABA signaling pathway.

One of the main responses activated by ABA is the closing of stomata, small openings in leaves that regulate gas exchange between the individual and the environment and control water loss.

However, if these receptors remain active for too long, the plant may suffer damage. It is as if it were in a permanent state of alert. “Imagine a system that is always responding at random. In this case, energy is wasted, which is what the plant does not want. Furthermore, the system becomes inefficient because it cannot perceive new stress situations,” explains the biologist.

To solve the problem, something scientists call “feedback “negative”, a regulatory model through which the signaling pathway itself activates mechanisms that attenuate the response to the signal. In this way, the activity of the signaling pathway is reduced through the pathway itself, avoiding excessive responses. This mechanism limits the negative side effects of prolonged ABA activation and allows the pathway to be “reset” so that the plant can respond appropriately to new stress situations in the future.

Investigating which elements are involved in this response, the researcher discovered that a microRNA, microRNA5628 (miR5628), inactivates the PYL6 receptor, one of the 14 ABA receptors in the species. Arabidopsis thaliana.

“This occurs because miR5628 specifically recognizes PYL6 messenger RNA [mRNA], promoting its cleavage. After cleavage, the mRNA is degraded by other post-transcriptional regulatory mechanisms, which, in the case of PYL6, are described in our paper.”

Since PYL6 mRNA is essential for the production of PYL6 protein, its degradation by miR5628 leads to reduced levels of this protein. As a consequence, responses to ABA are reduced.

“If ABA signaling becomes less active, it is as if this system were turned off in response to the action of miR5628,” explains the biologist.

Professor Michel Vincentz, who is the doctoral advisor and also the author of the article, emphasizes that the research is part of the objectives of the Plant Genetics Laboratory, which he coordinates. “We seek to understand how higher plants manage energy resources efficiently to optimize their development and vigor,” he points out.

Vieira's doctorate sought to verify the organism's ability to deal with adverse external situations by promoting internal adjustments and maintaining stability, a process called homeostasis. The research focused on ABA signaling.

For this, the species Arabidopsis thaliana was used. Just as rats serve as a model for animal studies, the Arabidopsis thaliana is a model widely used in the case of higher plants. “It is a model plant, which allows us to ask precise questions, because there is all the basic information [e.g. detailed genome] for all of this and there is also ample information and genetic material available.”

Although miR5628 is only present in the species studied, the research contributes to a deeper understanding of the strategies of plants when faced with environmental stress. “We are contributing to a better understanding of how the pathways that control the stress response are regulated. We need to have evidence to begin thinking about precisely manipulating these pathways using gene editing approaches. This microRNA is exclusive to this species. But I would not be surprised if there are other plants that develop the same type of mechanism or even more sophisticated mechanisms, because the evolutionary process is extremely dynamic,” emphasizes the professor. 

The role of microRNAs

In 1993, scientists first described a microRNA from a nematode—a tiny, 1-millimeter-long worm that eats bacteria—of the species Caenorhabditis elegans. The people responsible for this discovery, Victor Ambros and Gary Ruvkun, won the Nobel Prize in Medicine in 2024. MicroRNAs control gene expression, acting on the production of proteins and, thus, on ways of deactivating genes. They are present in plants and animals and function as essential regulators of several functions, such as development, growth, physiology, metabolism and responses to stress.

In the plant Arabidopsis thaliana, microRNA5628 was discovered in 2012. However, until Vieira's work, it was not known what functions it might have. "No target for this microRNA had been proposed in vivo, barely in silico [computer simulation]. We were able to validate the first target of this microRNA in Arabidopsis. "

In addition to Vieira and Vincentz, the authors of the article are researchers Américo Viana, Cleverson Matiolli, Gustavo Duarte and Raphael Campos, also from the Plant Genetics Laboratory (CBMEG); Renato Vincentini, coordinator of the Bioinformatics and Systems Biology Laboratory (CBMEG); Lucas Canesin, from the Center for Research in Genomics for Climate Change (CBMEG); and professors Fábio Nogueira and Carlos Barrera-Rojas, from the Laboratory of Molecular Genetics of Cultivated Plants at the University of São Paulo (USP).