Plant–Plant Communication: Is There a Role for Volatile Damage-Associated Molecular Patterns?

Abstract

Damage-associated molecular patterns (DAMPs) are an ancient form of tissue-derived danger or alarm signals that initiate cellular signaling cascades, which often initiate defined defense responses. A DAMP can be any molecule that is usually not exposed to cells such as cell wall components, peptides, nucleic acid fragments, eATP and other compounds. DAMPs might be revealed upon tissue damage or during attack. Typically, DAMPs are derived from the injured organism. Almost all eukaryotes can generate and respond to DAMPs, including plants. Besides the molecules mentioned, certain volatile organic compounds (VOCs) can be considered as DAMPs. Due to their chemical nature, VOCs are supposed to act not only locally and systemically in the same plant but also between plants. Here, we focus on damage-induced volatiles (DIVs) that might be regarded as DAMPs; we will review their origin, chemical nature, physiochemical properties, biological relevance and putative function in plant-plant communications. Moreover, we discuss the possibility to use such airborne DAMPs as eco-friendly compounds to stimulate natural defenses in agriculture in order to avoid pesticides.

Threat at One End of the Plant: What Travels to Inform the Other Parts?

“…Volatiles also offer the possibility to transfer information from one plant to neighboring plants or within the entire community [ 140 , 141 ]. Therefore, they play important roles for shaping plant communities and are the result of a long co-evolution of the community members, or interacting organisms (for ecological details, see References [ 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 ]). Volatiles belong to various chemical classes, such as terpenoids, benzenoids, phenylpropanoids and fatty acid-derived molecules, as well as minor classes such as nitriles, (ald)oximes and sulfides [ 140 ].…”

“…Emission of volatiles in response to damage or other types of threat is well known. Examples are green leaf volatiles [ 148 , 149 ] (such as ( Z )-3-hexenal, ( E )-2-hexenal, ( Z )-3-hexen-1-ol or ( Z )-3-hexen-1-yl-acetate) deriving from the oxylipin biosynthesis pathway, terpenes from the plastid-localized methylerythriol-phosphate and the cytosolic mevalonate pathways and aromatic phenylpropanoids and benzenoids from the shikimate pathway, which also includes MeSA. For none of the volatiles (except ethylene) a perception system is known at the molecular level yet.…”

“…For none of the volatiles (except ethylene) a perception system is known at the molecular level yet. However, as recently summarized in [ 149 ] the defense-related volatiles trigger downstream responses, such as [Ca 2+ ] cyt elevation; ROS production; MAP-kinase activation; defense gene expression, including genes for jasmonate and SA biosynthesis and signaling. The responses are identical in local and systemic tissues, but also along the traveling path.…”

Structural Diversity and Highly Specific Host-Pathogen Transcriptional Regulation of Defensin Genes Is Revealed in Tomato

“…To increase the likelihood of survival and successful reproduction, they need to develop countermeasures. As a result, the evolutionary race against pathogens and the struggle to endure adverse environmental conditions have resulted in the development and establishment of several defense mechanisms against these threats [ 1 , 2 ]. Furthermore, punctual mobilization of a multi-level response can be critical for survival.…”

“…These structures are chemically categorized as lipopolysaccharides, peptides (elongation factors, elicitins, and flagellin), peptidoglycans, or polysaccharides (chitin fragments) [ 7 ]. In addition, plants can identify Damage-Associated Molecular Patterns (DAMPs) that are host biomolecule derivatives, indicative of cellular damage [ 2 ]. DAMPs are usually cytosolic or nuclear proteins that are apoplastically exposed and denatured upon infection.…”