The plant photoreceptors are proteins connected to a light-sensing chromophore, which absorb photon of specific wavelength, inducing confirmational modification in the receptor protein that converts electromagnetic energy into biochemical potential (Folta and Carvalho 2015). Light regulates motility, adherence and virulence of plant pathogen (Wu et al., 2013; Galle et al., 2021). Pathogen associated molecular pattern (PAMP)-triggered immune responses are modulated by circadian clock and allows plants to anticipate and respond effectively to pathogen challenges during daytime (Bhardwaj et al., 2011). Plant have increased defense capability during daytime but in dark plant responses are weakened to a variety of pathogens leading to high incidence of disease (Yang et al., 2015).
Phytochrome can modulate plant immunity. The plant associated bacteria and fungi, their molecular mechanism of red-light sensing is by phytochrome and blue light sensing by LOV (light-oxygen-voltage)-domain proteins (Beattie et al., 2018). The photoconversion of the two phytochrome forms: The red light absorbing form (Pr) is inactive form which is converted to the active far-red light absorbing form (Pfr) on red light illumination and far- red light exposure converts it back into the inactive form Pr (Demotes-Mainard et al., 2016). Phytochrome-like histidine kinases are photoreceptors in number of fungi and bacteria. The gene encoding histidine kinases is required for normal vegetative growth, sclerotia production and pathogenicity in Botrytis cinerea (Hu et al., 2014). Disruption in this gene by homologous recombination may lead to reduction in vegetative growth, sclerotia production and pathogenicity of B. cinerea (Hu et al., 2014). Phytochrome in fungi is critical to reveal the genetic basis of the asexual and sexual switch responsible for fungal growth and distribution of plant pathogens (Wang et al., 2016). A brief exposure to red light during dark interval may be as effective as continuous illumination in suppressing sporulation of Podosphaera pannosa causing powdery mildew disease in greenhouse rose plant (Suthaparan et al., 2010).
Red light influence plant defense mechanisms against different plant pathogens. Plant grown under red light were more resistant to powdery mildew disease in cucumber plant, as exposure to red-light enhanced salicylic acid (SA) and hydrogen peroxide production as well as stronger expression of pathogenesis related-1 (PR-1) protein (Wang et al., 2010). The effect of SA on red light-induced resistance in broad beans infected by Botrytis cinerea was investigated by Khanam et al.(2005). The lesion formation and fungal development were suppressed on broad bean leaves infected with B. cinerea kept under red light. The resistance to B. cinerea is enhanced by increased activity of catalase a hydrogen peroxide scavenger under red light, whereas SA inhibits catalase-dependent resistance by enhancing the generation of hydrogen peroxide. The SA-dependent signaling pathway in broad bean may play a different role (Khanam et al., 2005).
Phytochrome signaling pathway modulates plant sensitivity to SA. Tomato plants grown under green and red light suppress disease development by regulating defense-related gene expression (Nagendran and Lee 2015). Red light induced resistance to Pseudomonas syringae pv. tomato is salicylic acid dependent (Islam et al., 2008). Exposing plant to red light increases SA level and induces SA signaling, mediating the production of reactive oxygen species (Galle et al., 2021). Fungal species display some form of light response ranging from metabolic reprograming to pathogenesis. The formation of infection hypha from appressoria of Botrytis cinerea was inhibited by red light(Islam et al., 1998). Yang et al.(2015) demonstrated red light can enhance the plant defense against pathogen infection; the effect of red light was associated with differentially expressed genes, particularly those involved in the circadian rhythm, photosynthesis, reactive oxygen species (ROS), calcium signaling and hormone regulation. High level of PR gene expression is correlated with an increase in plant resistance. The phytochrome pathway influences SA-dependent expression of PR-1 and therefore can influence the efficacy of plant defense reaction (Genoud et al., 2002). Red light radiation activated production of antifungal substances in broad bean leaf which is responsible for induced resistance of broad bean against B. cinerea (Islam et al., 1998). Low red:far-red light ratio enhances plant susceptibility to pathogens via modulation of defense hormone-mediated responses (Courbier et al., 2020). Release of asexual spore of Magnaporthe oryzae causing rice blast disease is controlled by both blue as well as by red light (Lee et al., 2006).
Tomato plant exposed to green and red light significantly reduced disease. Red light increases resistance of tomato plant to infection caused by Pseudomonas cichoriiJBC1 (Nagendran and Lee 2015). Cucumber plant when exposed to red light enhanced resistance against Sphaerotheca fuliginea Correlating that exposure to red light enhanced level of hydrogen peroxide, salicylic acid and stronger expression of defense related gene such as PR-1 (Wang et al., 2010). Similarly red light defends rice plant from Magnaporthe grisea. Red light activated tryptamine pathway and catalase inhibition that is involved in induction of resistance (Ueno et al., 2007).
References:
Beattie, G. A., Hatfield, B. M., Dong, H. and McGrane, R. S. 2018 Seeing the Light: The Roles of Red and Blue Light Sensing in Plant Microbes. Annu. Rev. Phytopathol. 56: 41 – 66
doi: 10.1146/annurev-phyto-080417-045931
Bhardwaj, V., Meier, S., Petersen, L. N., Ingle, R. A. and Roden, L. C. 2011 Defense Responses of Arabidopsis thaliana to Infection by Pseudomonas syringae are Regulated by the Circadian Clock. PLoS 6(10):e26968
doi: 10.1371/journal.pone.0026968
Courbier, S., Grevink, S., Sluijs, E., Bonhomme, P-O., Kajala, K., Van Wees, S. C. M. and Pierik, R. 2020 Far-Red Light Promotes Botrytis cinerea Disease Development in Tomato Leaves Via Jasmonate-Dependent Modulation of Soluble Sugars. Plant Cell Environ. 43(11): 2769 – 2781
doi: 10.1111/pce.13870
Demotes-Mainard, S., Peron, T., Corot, A., Bertheloot, J., Le Gourrierec, J., Pelleschi-Travier, S., Crespel, L., Morel, P., Huche-Thelier, L., Boumaza, R., Vian, A., Guerin, V., Leduc, N. and Sakr, S. 2016 Plant responses to red and Far-Red Light Application in Horticulture. Env. Exp. Bot. 121: 4 – 21
doi.org/10.1016/j.envexpbot.2015.05.010
Click to access 1-s2.0-s0098847215000933-main.pdf
Folta, K. M. and Carvalho, S. D. 2015 Photoreceptor and Control of Horticultural Plant Traits. Horticulture Science 50(9): 1274 – 1280
doi.org/10.21273/HORTSCI.50.9.1274
Galle, A., Czekus, Z., Toth, L., Galgoczy, L. and Poor P. 2021 Pest and Disease Management by Red Light. Plant Cell Environ. 44(10): 3197 – 3210
doi.org/10.1111/pce.14142
Genoud, T., Buchala, A. J., Chua, N-H. and Metraux, J-P. 2002 Phytochrome Signaling Modulates the SA-Perceptive Pathway in Arabidopsis. The Plant Journal 31(1): 87 – 95
doi.org/10.1046/j.1365-313X.2002.01338.x
Hu, Y., He, J., Wang, Y., Zhu, P., Zhang, C., Lu, R. and Xu, L. 2014 Disruption of Phytochrome-like Histidine Kinase Gene by Homologous Recombination Leads to a Significant Reduction in Vegetative Growth, Sclerotia Production and the Pathogenicity of Botrytis cinerea. Physiol. Mol. Plant Pathol. 85(pt 10): 25 – 33
doi: 10.1016/j.pmpp.2013.12.002
Islam, S. Z., Babadoost, M., Bekal, S. and Lambert, K. 2008 Red Light-Induced Systemic Disease Resistance against Root-knot Nematode Meloidogyne javanica and Pseudomonas syringae pv. tomato DC 3000. J Phytopathol. 156(11-12): 708 – 714
doi.org/10.1111/j.1439-0434.2008.01435.x
Islam, S. Z., Honda, Y. and Arase, S. 1998 Light-Induced Resistance of Broad Bean against Botrytis cinerea. J Phytopathol. 146(10): 479 – 485
doi.org/10.1111/j.1439-0434.1998.tb04609.x
Khanam, N. N., Ueno, M., Kihara, J., Honda, Y. and Arase, S. 2005 Suppression of Red Light-Induced Resistance in Broad Beans to Botrytis cinerea by Salicylic Acid. Physiol. Mol. Plant Pathol. 66(1-2): 20 – 29
doi.org/10.1016/j.pmpp.2005.03.006
Lee, K., Singh, P., Chung, W-C., Ash, J., Kim, T. S., Hang, L. and Park, S. 2006 Light Regulation of Asexual Development in the Rice Blast Fungus Magnaporthe oryzae. Fungal Genet. Biol. 43(10): 694 – 706
doi: 10.1016/j.fgb.2006.04.005
Nagendran, R. and Lee, Y. H. 2015 Green and Red Light Reduces the Disease Severity by Pseudomonas cichorii JBC1 in Tomato Plants by Upregulation of Defense-Related Gene Expression. Phytopathology 105: 412 – 418
doi.org/10.1094/PHYTO-04-14-0108-R
Suthaparan, A., Torre, S., Stensvand, A., Herrero, M. L., Pettersen, R. I., Gadoury, D. M. and Gislerod, H. R. 2010 Specific Light-Emitting Diodes can Suppress Sporulation of Podosphaera pannosa on Greenhouse Roses. Phytopathology 94(9): 1105 – 1110
doi.org/10.1094/PDIS-94-9-1105
Ueno, M., Imaoka, A., Kihara, J. and Arase, S. 2007 Effects of Light Quality on Induction of Tryptamine-Mediated Resistance in Lesion Mimic Mutant of Rice Infected with Magnaporthe grisea. J Phytopathol. 155(4): 228 – 235
doi.org/10.1111/j.1439-0434.2007.01222.x
Wang, H., Jiang, Y. P., Yu, H. J., Xia, X-J., Shi, K., Zhou, Y. H. and Yu, J. Q. 2010 Light Quality Affects Incidence of Powdery Mildew Expression of Defense-Related Genes and Associated Metabolism in Cucumber Plants. Eur. J. Plant Pathol. 127(1): 125 – 135
doi: 10.1007/s10658-009-9577-1
Wang, Z., Li, N., Li, J., Dunlap, J. C., Trail, F. and Townsend, J. P. 2016 The Fast-Evolving Phy-2 Gene Modulates Sexual Development in Response to Light in the Model Fungus Neurospora crassa. mBio. 7(2): e02148
doi: 10.1128/mBio.02148-15
Wu, L., McGrane, R. S. and Beattle, G. A. 2013 Light Regulation of Swarming Motility in Pseudomonas syringae Integrates Signaling Pathways Mediated by a Bacteriophytochrome and a LOV Protein. mBio 4(3): e00334-13
doi: 10.1128/mBio.00334-13
Yang, Y-X., Wang, M-M., Yin, Y-L., Onac, E., Zhou, G-F., Peng, S., Xia, X-J., Shi, K., Yu, J-Q and Zhou, Y-H. 2015 RNA-seq Analysis Reveals the Role of Red Light in Resistance against Pseudomonas syringae pv. tomato DC3000 in Tomato Plants. BMC Genomics 16: 120
doi.org/10.1186/s12864-015-1228-7
BIOLOGICAL PROCESSES- A NATURE'S GIFT 