Reactive Oxygen Species Play a Role in the Infection of Rice by Bacterial Leaf Blight Pathogen Xanthomonas oryzae pv. oryzae

Author: Swathi S. Patil, M.K. Prasannakumar and Ramu S. Vemanna

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Abstract

Xanthomonas oryzae pv. oryzae (Xoo) causing bacterial leaf blight of rice is a global problem in rice production. Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses including pathogen attack trigger excessive production of ROS causing progressive oxidative damage leading to programmed cell death and ultimately activating the host defense responses. Inoculation of Xoo by leaf clipping method resulted in more lesion length in the susceptible cultivar TN-1 compared to resistant cultivar BPT-5204. Further, quantification of ROS viz., Hydrogen peroxide (H2O2) and Superoxide (O2¯) by 3, 3- Diaminobenzidine (DAB) and Nitro blue tetrazolium (NBT) assays respectively showed increased levels of both H2O2 and O2- in the resistant cultivar BPT-5204 at 6 days post inoculation (dpi) and it was highest in the leaf tissues collected at 10dpi. The levels of H2O2 and O2- decreased significantly after 2 dpi in the control plants of both cultivars BPT-5204 and TN-1. In the susceptible cultivar TN-1, the levels of H2O2 and O2- decreased significantly from 4dpi. There was 78% fold increase in the production of H2O2 and 70% fold increase in the production of O2- in the resistant cultivar compared to the susceptible cultivar. Oxidative burst or the rapid production of ROS in response to pathogenic invasion aids the host plant in establishing various defensive barriers against infections. As a result, pathogen infections cause rapid accumulation of ROS, which are important in restricting pathogenic entry, inducing signal transduction of various defence responses or programmed cell death. We speculate that the increased production of the ROS viz., H2O2 and O2- in the resistant variety trigger the defense pathways in the host and thereby limit the disease.

Keywords

Xanthomonas oryzae pv. oryzae, Reactive oxygen species, hydrogen peroxide, superoxide

Conclusion

In nature, plants develop in complex and adaptive environments. Plants must therefore respond efficiently to environmental stressors to maintain homeostasis and enhance their fitness. ROS are considered a double-edged sword for plant life since they regulate various processes such as cell wall synthesis, defense against pathogens, plant aging and programmed cell death, and the behavior of stomata (Chitranashi et al., 2022). Reactive oxygen species (ROS) function as critical, fast-acting orchestrators that link biotic responses to plant homeostasis and development (Berrios and Rentsch 2022). Plants respond to pathogen invasion through activation of oxidative burst, which leads to the production of reactive oxygen species (ROS), including superoxide (O2) and hydrogen peroxide (H2O2). The production of reactive oxygen species (ROS) is one of the earliest cellular responses following successful pathogen recognition (Mittler, 2017). Thus, ROS production during oxidative burst helps the plants to restrict further spread of the invading pathogens by inducing HR or plant immune responses (Durrant and Dong 2004). We quantified the ROS production in resistant as well as susceptible rice cultivars, particularly in the production of H2O2 and O2 during rice: Xoo interaction. The resistant cultivar BPT-5204 produced H2O2 and O2 significantly higher compared with the susceptible cultivar TN-1. This may be due to Xa genes present in BPT-5204 that contribute to the oxidative burst during pathogenesis by Xoo and thereby reducing the infection rate of Xoo. ROS are regarded as beneficial messengers that trigger oxidative signalling, systemic acquired acclimation, and systemic acquired resistance. Despite the scientific progress made during the last two decades, the mode of action of ROS is still far from being fully understood. Further elucidation of the genes involved in ROS production and signaling provide doorway to develop varieties resistant to bacterial infection.

References

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How to cite this article

Swathi S. Patil, M.K. Prasannakumar and Ramu S. Vemanna (2023). Reactive Oxygen Species Play a Role in the Infection of Rice by Bacterial Leaf Blight Pathogen Xanthomonas oryzae pv. oryzae. Biological Forum – An International Journal, 15(2): 1107-1113.