**5. Conclusions**

The main findings of this study shed light on the role of light quality and reveal a possible mechanistic control of photoreceptors on the signaling transduction that activates the plant genetic resources to respond to the *E. amylovora* pathogen attack via a large array of transcription factors. CRY1 has an agonistic role in the activation of *PR* genes, during the interaction of host-pathogen, and an antagonistic role in the *E. amylovora* growth. These results suggest that a possible escape signal joined to circadian and ultradian rhythms could be connected to the regulome of PR proteins synthesis under BL and their photosensor, which might play a relevant role in plants grown in an orchard. Moreover, the results provide new knowledge on fire blight control methods targeting the plant light regulation systems. The sensitivity of the *E. amylovora* to monochromatic radiation could use LED technology for sustainable and non-invasive pathogen control. New scenarios in plant pathology control systems through th77e defense gene activation by light and negative regulation of pathogen virulence could be operational in the frame of optogenetic control [74].

To our knowledge, no previous study has addressed the effect of the environmental spectral quality's radiation constraints on the activation of the genes involved in plantpathogen interaction. It remains to be found whether or not SA, JA, and ethylene genes play a role in the blue-light signaling (COP1, HYH, SPA1) and if they have a regulatory relationship with CRY1. Future studies could focus on the use of light quality, in particular BL, as an elicitor to set up protection methods for fruit crop trees, in the nursery and orchard, against fire blight.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/ 10.3390/plants10091886/s1, Figure S1: Representative scheme of the sampling time point used to evaluate the PR genes expression in Dar Gazi-wt grown under white light, Figure S2: Representative scheme of the sampling time point used to evaluate the *PR* genes expression in *Dar Gazi-wt* exposed for 24 h under continuous lightness (a) and continuous darkness (b), Figure S3: Representative scheme of the sampling time point used to evaluate the *PR* genes expression in *Dar Gazi-wt*, *Dar Gazi-phyB* and *Dar Gazi-cry1* plants grown in exposed for 24 h under continuous WL, RL, FRL or BL, Figure S4: Dar Gazi events of regenerations after 25 days in dark condition (a). Shoots were transferred to the medium, containing kanamycin, to select putative transgenic lines, and subcultured four/five times for rapid and clonal multiplication (b). The medium used for the in vitro selection of regenerated buds was enriched with 100 mg/L Kanamycin. (c) Plantlets of transgenic lines during proliferation state, Figure S5: Detection of *ef1A* gene fragments in cDNA of *Dar Gazi-wt*, *Dar GaziphyB,* and *Dar Gazi-cry1* plants (a). M: Ladder; WT: *Dar Gazi-wt*; phyB*: Dar Gazi-phyB*; cryI: *Dar Gazi-cry1*; B: Blank. Detection of *NptII* gene fragments in cDNA of *Dar Gazi-wt*, *Dar Gazi-phyB,* and *Dar Gazi-cry1* plants (b). M: Ladder; WT: *Dar Gazi-wt*; phyB: *Dar Gazi-phyB*; cryI: *Dar Gazi-cry1*; B: Blank, Figure S6: Detection of *AtPHYB*, using specific primers for *A. thaliana PHYB* that amplify the *AtPHYB* gene fragments only in cDNA of *Dar Gazi-phyB* plants (a). M: Ladder; WT: *Dar Gazi-wt*; phyB: *Dar Gazi-phyB*; cryI: *Dar Gazi-cry1*; B: Blank. Detection of *LeCRYI*, using specific primers for *L. esculentum CRYI* that amplify the cryILE gene fragments in cDNA of *Dar Gazi-cry1* plants (b). M: Ladder; WT: *Dar Gazi-wt*; phyB: *Dar Gazi-phyB*; cryI: *Dar Gazi-cry1*; B: Blank, Table S1: Sequence of primers used to validate the molecular insertion of *AtPHYB* and *LeCRY1* in pear genome.

**Author Contributions:** T.S., C.I., B.T., M.R. and R.M. (Rosario Muleo) contributed to the conception and design of the study. T.S., I.F., C.I., F.L., M.R. and R.M. (Rosario Muleo) contributed to defining the methodology. T.S., I.F., F.L., R.M. (Roberto Mancinelli), M.R. and R.M. (Rosario Muleo) contributed to data formal analysis. T.S., C.I., F.L., B.T., M.R. and R.M. (Rosario Muleo) contributed to the investigation. T.S., I.F. and R.M. (Rosario Muleo) wrote the first draft of the manuscript. T.S., I.F., C.I., R.M. (Roberto Mancinelli), B.T., M.R. and R.M. (Rosario Muleo) wrote and edited the final version of the manuscript. All authors contributed to the article and approved the submitted version. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
