Research Projects on Polyamines

The proposal is committed to the use of polyamines for developing improved crop genotypes with enhanced disease resistance and new, environmentally compatible plant protection products adapted to the circular economy. Given the importance of Botrytis cinerea and Pseudomonas syringae infections in agriculture, and their contrasting life-style strategies, these pathogens are included to develop new disease resistance strategies and to understand the molecular mechanisms underlying such effects.

Polyamines are stress-inducible metabolites that play a crucial role in plant disease resistance through mechanisms that are just beginning to be understood. The modulation of cell death by polyamines is an important mechanism conditioning plant disease outcomes, particularly influencing the success of infection by necrotrophic pathogens. The pathogenic life-style (necrotrophs vs. hemibiotrophs) is crucial when investigating the effects of cell death on disease resistance.

Studies on the modulation of defense-related cell death by polyamines have primarily focused on the production of reactive oxygen species (ROS) due to polyamine oxidation. However, our previous data demonstrate that the effect of polyamines on cell death is not solely explained by ROS production. Evidence points to polyamines acting as double-edged swords, showing pro-cell death or pro-survival effects depending on the pathogen life-style, the nature of the polyamine, and its concentration. By understanding the mechanisms through which polyamines influence the cell's fate from survival to death, we can fine-tune polyamine metabolism to improve plant disease resistance to different life-style pathogens.

We hypothesize that polyamines can modulate cell death execution through their participation in effector-triggered immunity (ETI), calcium signaling, autophagy, and ROS signaling. Additionally, evidence indicate that polyamines crosstalk with jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) biosynthesis and signaling, conditioning defense outputs to contrasting life-style pathogens.

The modulation of cell death by polyamines can also be elucidated through the combined use of forward genetics and genetics of natural variation, along with holistic approaches using untargeted omics that provide an integrative view from a molecular perspective. Given the importance of programmed cell death (PCD) modulation in plant disease resistance, this proposal will reveal the fundamental mechanisms underlying the modulation of PCD by polyamines and how this can be used to generate crops resistant to hemibiotrophic and necrotrophic pathogens.

As proof-of-concept, the project will perform targeted modifications of polyamine metabolism in tomato and test their effects on disease resistance to contrasting life-style pathogens (P. syringae and B. cinerea). We will also develop new plant protection products based on polyamines derived from agrifood by-products as natural sources, which will be tested in tomato for their effects on enhancing resistance to these pathogens.

Polyamines are low molecular weight compounds that accumulate during defense. In plants, most abundant polyamines are the diamine putrescine, triamine spermidine, tetraamine spermine and its isomer thermospermine. These compounds can be found in free forms, acetylated or conjugated to hydroxycinnamic acids, proteins or cell wall constituents. Polyamines can be oxidatively deaminated by amine oxidases, generating hydrogen peroxide, which might trigger ROS-dependent signaling. 

Despite the body of evidence about the involvement of polyamines in plant defense, the detailed molecular mechanisms and pathways mediating polyamine-triggered defense signaling are just beginning to be revealed. In this proposal we will perform a comprehensive study about polyamine signaling during defense in both local and systemic tissues. We argue that local and systemic responses cannot be disentangled in the defense response, as it is part of an integrated and coordinated response to environmental stimuli. We recently reported that the polyamine putrescine, which accumulates during defense, contributes to the ROS-dependent amplification of pathogen associated molecular pattern (PAMP)-triggered immunity and effector triggered immunity (ETI) leading to local salicylic acid (SA) biosynthesis. Interestingly, we also found that putrescine triggers systemic transcriptional responses overlapping with systemic acquired resistance (SAR) activation, although the mechanisms by which Put activates SAR remain unknown. Here, we will investigate the molecular mechanisms by which putrescine, ROS and/or derived metabolites contribute to SAR establishment and systemic signaling through genetic, molecular and metabolomics analyses. In addition, we're studying the contribution of polyamines to cell wall integrity signals triggering defense elicitation.

Key publications:

• Zhang C., Atanasov K.E., Alcázar R. (2023) Spermine inhibits PAMP-induced ROS and Ca 2+ burst and reshapes the transcriptional landscape of PTI in Arabidopsis. J Exp Bot. 74: 427-442

• Zhang C., Atanasov KE, Murillo E, Vives-Peris V, Zhao J, Deng C, Gómez-Cadenas A, Alcázar R (2023) Spermine deficiency shifts the balance between jasmonic acid and salicylic acid-mediated defence responses in Arabidopsis. Plant, Cell & Environ.  https://doi.org/10.1111/pce.14706

Polyamines are small protonated amines present in all living organisms. Most abundant polyamines are the diamine putrescine, triamine spermidine and tetraamine spermine and its isomer thermospermine. Polyamine accumulation is one of the most conserved metabolic hallmarks during plant stress. Genetic approaches in the recent years have demonstrated a role for polyamines on protection against abiotic stresses, such as salinity, freezing and drought. However, little is known about their contribution and mode of action during plant defense. We investigate the roles of polyamines in plant defense and plant-microbe interactions, and the involvement of oxidative-dependent pathways on such responses. Through a genetic-based approach, we’re studying the biological implications for polyamines during defense. We’re also identifying the genetic components involved in polyamine signaling, transport or perception. We argue that such type of genetic approaches are missing and are required to establish mechanistic processes for plant polyamines. Finally, we’re studying the roles of polyamines in shaping the microbial composition of the plant rhizosphere. Overall, our research provides an integrative view of plant polyamines in the context of plant-pathogen and plant-microbe interactions. 

Key publications

Plant biostimulants improve nutrient uptake and use efficiency, thus reducing the need to apply high concentrations of chemical fertilizers. Aiming at the transition towards a more sustainable agriculture in the context of climate change, we're developing new microbe-based biostimulant products that are being tested in different crops under diverse stress conditions. This proof-of-concept project is being performed in close collaboration with the Transfer of Technology Office of the University of Barcelona. 

Our lab is also collaborating with industrial partners interested in the development of new biostimulant products.

Key publications