Biotic stress deleteriously affects growth, development, and productivity in plants. Proline (Pro) plays a significant role in enhancing plant resistance to pathogen infection. However, its effects on reducing Lelliottia amnigena-induced oxidative stress in potato tubers remain unknown. The present study aims to evaluate the in vitro Pro treatment in potato tubers exposed to a newly emerging bacterium, L. amnigena. Sterilized healthy potato tubers were inoculated with 0.3 mL of L. amnigena suspension (3.69 × 107 CFU mL-1) 24 h before Pro (5.0 mM) application. The L. amnigena treatment significantly increased the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2) in the potato tubers by 80.6 and 85.6%, respectively, compared to the control. Application of proline (Pro) decreased MDA and H2O2 contents by 53.6 and 55.9%, respectively, compared to the control. Application of Pro to L. amnigena-stressed potato tubers increased the activities of NADPH oxidase (NOX), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), 4-coumaryl-CoA ligase (4CL) and cinnamate-4-hydroxylase (C4H) C4H by 94.2, 96.3, 97.3, 97.1, 96.6, 79.3, 96.4, 93.6, and 96.2%, respectively, compared to the control. In comparison to the control, the genes PAL, SOD, CAT, POD, and NOX were significantly increased in the Pro-treated tubers at 5.0 mM concentration. Tubers treated with Pro + L. amnigena increased the transcript levels of PAL, SOD, CAT, POD, and NOX by 2.3, 2.2, 2.3, 2.5, and 2.8-fold respectively, compared to the control. Our findings suggested that pretreatment of tubers with Pro might reduce lipid peroxidation and oxidative stress by enhancing enzymatic antioxidant activity and gene expression.
Keywords: Antioxidant enzymes; Gene expression; Pathogen; Proline; Reactive oxygen species.
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