Fig. 5. Model of the mechanisms involved in mechanical injury response and its alteration by arthropod attack.

A Model of the cellular response to Mechanical Injury (MI). 1. Cartoon of a T. atroviride hypha. 2. Early cellular response to MI (0–90 min) after damage. (a) After mechanical injury, damaged cells release ATP molecules, which are recognized by putative receptors localized in the cell membrane; (b) recognition of extracellular ATP allows influx of extracellular calcium (c), which promotes increases in cytosolic calcium concentration (d; [15]). ATP recognition activates the MAPK Tmk1 (e) that in turn activates the DNA damage response (f; [15]) (g). Extracellular ATP can also be recognized by a GPCR (h). The GPCR, activates the NADPH oxidase Nox1 (I; [17]). O₂^- produced by Nox1 (j) is converted to H₂O₂ by a superoxide dismutase (k). ROS activates Tmk3 (l) that triggers the chemical response to injury (m; [25]). 3. Hyphal regeneration is evident 1-2 h after MI. 4. Activation of the het and secondary metabolism-related genes and cell growth. 5. Cell differentiation and sexual development is observed 24-48 h after mechanical injury (MI). B Impact of Drosophila attack on the response. 1. Cartoon of a T. atroviride hypha. 2. Early cellular response to larval grazing (0 to 90 min). (a) During larval grazing, larval salivary gland components such as proteases are released, inhibiting genes related to calcium signaling (b, c, d) and the MAPK tmk1 (e), consequently repressing the expression of DNA damaged (f) and regeneration (g) related genes. Grazing damage and the release of SGC increase ROS production and accumulation (h), which increases DNA damage (f), and contributes to inhibition of hyphal regeneration (g). Activation of the MAPK Tmk3 (i) is essential to trigger the chemical response to arthropod attack (j,[26]). SGC are recognized by lectins that could serve as a defense mechanism (k) 3. Inhibition of hyphal regeneration after Dm. 4. Activation of HET and SM related genes (red letters indicate that it is unclear when growth reinitiates). 5. Cell differentiation and asexual development processes observed 24–48 h after larval grazing. MI: mechanical injury, Dm: Grazing by D. melanogaster larvae. SGC: salivary gland components, Tmk1: MAPK Tmk1, Tmk3: MAPK Tmk3, RRP: Regeneration related processes, ROS: Reactive oxygen species, SM: Secondary metabolism, GPCR: G-Protein Coupled Receptors, Nox: NADHP oxidases, RRG: Regeneration-Related Genes. Model created in Biorender.com.