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A New Biostimulant to Enhance Tomato Chilling Stress Tolerance and Yield

In a groundbreaking study, researchers have identified two strains of Pararhizobium sp. (44 and 128) that significantly enhance chilling stress tolerance in tomato plants.

Tomato (Solanum lycopersicum L.), a subtropical crop, often struggles in temperate climates due to its sensitivity to low temperatures. This limitation has historically hindered tomato cultivation in colder regions, affecting crop yield and production.

The study revealed that inoculating tomato plants with Pararhizobium strains 44 and 128 activates the ICE1-CBF-COR cold stress signaling pathway, enhancing the plants’ ability to withstand chilling temperatures. This process also improves the plants’ reactive oxygen species (ROS) detoxifying capacity and boosts the production of stress-protective metabolites like polyamines and reduced glutathione (GSH).

Moreover, the treatment not only helps plants under stress conditions but also increases fruit weight and quality under normal conditions. These findings suggest that Pararhizobium strains 44 and 128 could be valuable biostimulants for improving both chilling stress tolerance and overall crop yield in tomato plants.

Chi Zhang succesfully defended her Thesis about "The contribution of the polyamine spermine to plant defense"  on July 11, 2024 10:00 h at the Aula Magna of the Faculty of Pharmacy and Food Sciences, Universitat de Barcelona.

The committee was constituted by Prof. José Moran (UPN), Dr. Antoni Garcia-Molina (IRTA-CRAG) and Prof. Teresa Altabella (UB).

Chi Zhang is holder of a Chinese Scholarshop Council PhD fellowsip. PhD Program: Biotechnology. Universitat de Barcelona

Climate change has brought about sudden temperature changes in recent decades, such as colder winters, and has also increased the frequency of droughts, which have a significant impact on farming yield. Researchers at the University of Barcelona (UB) have developed a tool to help fight these adverse effects. It is a new type of biostimulant that improves crop quality and also protects against cold and high salinity that comes with drought conditions. Plus, this innovative product has been proven to improve crop yield and quality in trials on tomato and rapeseed.

Biostimulants are organic blends of various plant extracts or products formulated using living micro-organisms that help plants grow by stimulating their metabolism. These characteristics have made them a more eco-friendly, organic alternative to synthetic fertiliser in recent years. Despite being extensively used in agriculture, chemical fertilisers can contaminate the soil, water and air, harming the environment and altering natural ecosystems.

The new biostimulant developed by the UB research group is based on new strains of Pararhizobium sp isolated and characterised in their lab. These biological stimulants can be an effective option that is more eco-friendly than current fertilisers, and can also be used alongside them, protecting crops and cutting down on synthetic fertilisers and their hazardous effects.

The team led by Professor Rubén Alcázar of the Department of Biology, Healthcare and the Environment in the Faculty of Pharmacy and Food Sciences has already successfully validated the efficacy of this new biostimulant in rapeseed and tomato crops. In tomatoes, the new product improved crop yield, made plants more tolerant to low temperatures and improved fruit quality. With rapeseed, the group observed increased performance, resistance to freezing temperatures and salinity tolerance.

Moreover, the product is easy to scale up as the strains are stable and their growth conditions are suitable for industrial use.

As such, a European patent application has already been submitted to protect the innovation and work is under way on new trials to validate the efficacy of the biostimulant in other crops.

Published in: FBG newsletter  Universitat de Barcelona News

In this new publication by Zhang et al. we report an unexpected effect of spermine depletion on activation of jasmonic acid biosynthesis and dampening of salicylic acid-mediated defenses in plant-bacteria interactions. The work, published as open access in the journal Plant, Cell & Environment is freely accessible here.

Authors of the work propose a model for the integration of spermine metabolism on salicylic acid and jasmonic acid defense responses. In this model, Spm deficiency results in increased levels of monogalactosyldiacylglycerol (MGDG) and increased expression of JA biosynthesis genes that correlate with elevated levels of JA under basal conditions and in response to Pst DC3000. Spm deficiency enhances ANAC019 expression in response to Pst DC3000, leading to a more robust deregulation of SA-metabolism genes ICS1 and BSMT1, and reduced SA content. This way, Spm deficiency shifts the balance between JA and SA, which associates with enhanced susceptibility to Pst DC3000 and disease resistance to B. cinerea. Spm deficiency also triggers endoplasmic reticulum (ER) stress signalling in response to Pst DC3000, which indicates the importance of this polyamine in alleviating ER stress during defence. 

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

Picture: Ester Murillo at the defense exposition in the Main Lecture Hall of the Faculty of Biology, Universitat de Barcelona. 20/10/2023

Chi Zhang and collaborators report the inhibitory effect of the polyamine spermine in the PAMP-elicited ROS burst mediated by RBOHD. This effect of spermine on ROS production reshapes the transcriptional reprogramming of PTI in Arabidopsis and has an impact on defense to pathogenic bacteria. Published in open access, the full story can be read here.

Reference: 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

January, 2023

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 project we will perform a comprehensive study about polyamine signaling during defense in both local and systemic tissues. 

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.

Proyecto PID2021-126896OB-I00 financed by MCIN/ AEI/10.13039/501100011033/ y FEDER “Una manera de hacer Europa”