Plant hormones (Literature sources on phytohormones and plant signalling)

Annual Review of Plant Biology (2024)

Abstract: "This review focuses on the intricate relationship between plant polyamines and the genetic circuits and signaling pathways that regulate various developmental programs and the defense responses of plants when faced with biotic and abiotic aggressions. Particular emphasis is placed on genetic evidence supporting the involvement of polyamines in specific processes, such as the pivotal role of thermospermine in regulating xylem cell differentiation and the significant contribution of polyamine metabolism in enhancing plant resilience to drought. Based on the numerous studies describing effects of the manipulation of plant polyamine levels, two conceptually different mechanisms for polyamine activity are discussed: direct participation of polyamines in translational regulation and the indirect production of hydrogen peroxide as a defensive mechanism against pathogens. By describing the multifaceted functions of polyamines, this review underscores the profound significance of these compounds in enabling plants to adapt and thrive in challenging environments."

Trends in Plant Science (2021)

Highlights: Polyamines (PAs) are a relatively overlooked component of the bacterial and plant metabolomes. The multiple roles of PAs have blurred our understanding of the function of these molecules in the context of plant–pathogen interactions. Plant PAs are involved in plant immunity, because they serve as essential modulators of the redox status of the cell, contributing to potentiation of the oxidative burst as well as the synthesis of other antimicrobial compounds. Perturbation of plant PA homeostasis appears as a common strategy of pathogens during infection. Several mechanisms involving pathogen effectors and phytotoxins lead to manipulation of plant PA biosynthetic pathways, although the outcome of these actions may have different purposes.

Abstract: "Polyamines (PAs) are ubiquitous amine molecules found in all living organisms. In plants, beside their role in signaling and protection against abiotic stresses, there is increasing evidence that PAs have a major role in the interaction between plants and pathogens. Plant PAs are involved in immunity against pathogens, notably by amplifying pattern-triggered immunity (PTI) responses through the production of reactive oxygen species (ROS). In response, pathogens use phytotoxins and effectors to manipulate the levels of PAs in the plant, most likely to their own benefit. It also appears that pathogenic microorganisms produce PAs during infection, sometimes in large quantities. This may reflect different infectious strategies based on the selective exploitation of these molecules and the functions they perform in the cell."

Scientia Horticulturae (2022)

Highlights: • Ethylene dictates fruit development/ripening and response to a/biotic stresses. • Ethylene arising from the peach-Monilinia spp. depends on the fruit developmental stage. • The species and virulence of Monilinia are key determining ethylene modulation/response. • Monilinia spp. produce ethylene under certain growing conditions. • An interplay exists between ethylene, ROS and polyamines during host-pathogen interactions.

Abstract: "It is already well known that ethylene plays a crucial role in peach fruit growth and ripening, by triggering an unset of biochemical and physiological changes that finally make the fruit attractive for consumption. This said, ethylene is not only responsible for fruit ripening but, in conjunction with other hormones, or key compounds (ROS, polyamines, etc.) is involved in the plant response to numerous abiotic stresses (drought, salt and heat tolerance) as well as the plant/fruit response against certain pathogens. Among peaches, one of the most devastating pathogens is the brown rot causing fungus Monilinia spp. that can affect the fruit both on the field or postharvest. Nonetheless scarce information exists regarding the Monilinia-peach interaction from a physiological and molecular perspective. In this sense, recent studies point out to the importance of ethylene during such interaction, which seems to be dependent on the fruit developmental stage and also on the Monilinia species or even the strain's virulence. Why the fruit or the fungus reacts different to distinct Monilinia species or strains and why such reaction depends on the fruit physiological stage is, however, still elusive. Accordingly, this review aims to shed light on the role of ethylene, alone or through a complex cross-talk with other compounds, not only during peach development and ripening but also during the Monilinia-peach interaction. Based on the available literature, it is clear that not only ethylene biosynthesis but ethylene signaling and the activation of ethylene response factors via ROS may play an essential role during this specific host-pathogen interaction."