Alleviation of allelochemical juglone-induced phytotoxicity in tobacco plants by proline

Figures & data

Figure 1. The effect of juglone treatment on growth of tobacco (Nicotiana benthamiana) seedlings and juglone induces reactive oxygen species (ROS) production in tobacco roots. (a) Five-day-old tobacco seedlings were transferred to Murashige and Skoog (MS) medium supplemented with concentrations of juglone. Seminal root lengths were measured after 5 days. Data are mean ± SD of three experiments. *p < 0.05 by paired t-test. Bar, 3 cm. (b) Root samples were labeled with 10 μΜ CM-H₂DCF-DA for 30 min, then treated with concentrations of juglone. Green fluorescence indicates the presence of ROS.

Figure 2. The effect of juglone on proline content and expression of proline metabolism genes in tobacco seedlings. (a) Five-day old tobacco seedlings were transferred to MS medium supplemented with or without 10 μM juglone. Proline content was determined after 5 days. Data are mean ± SD of three experiments. Means with the different letters are significantly different at p < 0.05 (ANOVA). (b) Gene expression in response to juglone treatment in tobacco shoots and roots. RT-PCR analysis of mRNA levels of genes related to proline synthesis pathway – pyrroline- 5-carboxylate synthetase (P5CS) and ornithine aminotransferase (OAT), proline dehydrogenase (PDH) – in tobacco shoots and roots during juglone treatment. Elongation factor 1 α (EF1-α) was an internal control.

Figure 3. Exogenous application of proline (pro) enhances tolerance to juglone (ju) in tobacco seedlings. (a) Length of seminal roots in tobacco seedlings measured after 5 days of juglone treatment. Data are mean ± SD of three experiments. Means with the different letters are significantly different at p < 0.05 (ANOVA) (b) Effect of proline treatment on 10-μM juglone-induced ROS accumulation in tobacco roots. Root samples pretreated or not with 100 μM proline for 3 h were treated with 10 μM juglone for 15 min.