Figure Legends
Figure 1. Wired and wireless phytobiome communication. Clonal plants (right) communicate via physical connections (e.g., stolons and rhizomes) or VOCs. Plants also communicate via dodder and mycorrhiza (left). Reciver plants can act as nodes to transfer defense signals against pests and pathogens to neighboring conspecific and heterospecific plants. Volatiles and root exudates recived by neighboring plants modulate receiver plant defense systems, attract parasitoids and entemopathogens, and induce plant microbiome remodeling to protect plants against imminent stress conditions.
Figure 2. Illustration of the signal input-transfer-output model in plantplant communication. Molecular patterns, volatiles, and effector proteins of pests and pathogens elicit plant signaling pathways that promote volatiles emission and root exudation. Plant signals can be delivered to neighboring plants through the atmosphere or soil (wireless communication), or transferred through mycorrhiza, fungi, and odder (wired communication). Signals can be converted to their active form by receiver plant proteins. Signal perception by neighbor plants activates signaling pathways and phosphorylation cascades, which subsequently induce the expression of defense-related proteins and metabolites. Signal perception also changes the root exudate and recruits beneficial microbes. MAMPs, microbe-associated molecular patterns; HAMPs, herbivore-associated molecular patterns; VOCs, volatile organic compounds; GLVs, green leaf volatiles; BZ, benzoxazinoid; SA, salicylic acid; MeSA, methyl salicylate; JA, jasmonic acid; MEP, methylerythritol phosphate; MVA, mevalonic acid; MAPKs, mitogen-activated protein kinases; TFs, transcription factors.
Figure 3. Signals from neighboring plants modulate signaling pathways in receiver plants and induce microbiome remodeling. Signals can be sensed by reciver proteins (e.g., ETR1 sensor for ethylene) or coverted to active signals [e.g., SABP2 for salicylic acid (SA)]. Signals are transmitted through well-characterized downstream pathways that may cross-talk with each other. These signaling pathways regulate defense mechanisms against different groups of attackers and induce plant microbiome remodeling by changing root exudation, thereby adapting the plant holobiome to respond to imminent threats. MeSA, methyl salicylate; SABP2, SA-BINDING PROTEINS 2; NPR, NON-EXPRESSER OF PR genes; G3P, glycerol-3-phosphate; ETR1, ETHYLENE RESPONSE 1; EIN2, ETHYLENE INSENSITIVE 2; CTR1, CONSTITUTIVE TRIPLE RESPONSE 1; ORA59, OCTADECANOID-RESPONSIVE ARABIDOPSIS 59; MeJA, methyl jasmonate; Med25, Mediator 25; JAZ, JASMONATE ZIM DOMAIN protein; SCFCOI1, Skp1-Cul1-F-box protein CORONATINE INSENSITIVE 1; FIT1, FE-DEFICIENCY-INDUCING TRANSCRIPTION FACTOR1; FRO2, FERRIC REDUCTASE OXIDASE 2; IRT1, IRON-REGULATED TRANSPORTER 1; IAA, indole-3-acetic acid; AUX1/LAX, AUXIN RESISTANT 1/LIKE AUX1; ALMT1, ALUMINUM-ACTIVATED MALATE TRANSPORTER; CDPK, Ca2+-dependent proteinkinases; CIPK, calcineurin B like proteins (CBL)-interacting protein kinase.