Salicylic acid regulates polyamine biosynthesis during drought responses in oat

Abstract

Salicylic acid (SA) is involved in several plant processes including responses to abiotic stresses. Although SA is thought to interact with other regulatory molecules in a complex way, currently, little information is available regarding its molecular mechanisms of action in response to abiotic stresses. In a previous work, we observed that drought-resistant oat plants significantly increased their SA levels as compared with a susceptible cultivar. Furthermore, exogenous SA treatment alleviated drought symptoms. Here, we investigated the interaction between SA and polyamine biosynthesis during drought responses in oat and revealed that SA regulated polyamine biosynthesis through changes in polyamine gene expression. Overall, SA treatment decreased the levels of putrescine under drought conditions while increased those of spermine. This correlates with the downregulation of the ADC gene and upregulation of the AdoMetDC gene. Based on the presented results, we propose that SA modulates drought responses in oat by regulating polyamine content and biosynthesis.

Keywords: Drought; oat; polyamine; salicylic acid.

Figure 1.

Effect of salicylate on polyamine content. Putrescine, spermidine, and spermine were measured in well-watered or droughted Flega (drought susceptible) and Patones (drought resistant) plants treated with salicylate 100 µM (black bars) or with the biologically inactive isomer 4-hydroxybenzoic acid (4-hBA) (control, white bars). Data are mean of five replicates ± standard error. * and ** indicate significant differences between treatments at p < 0.05 and 0.01, respectively.

Figure 2.

Effect of salicylate on the expression of several genes involved in polyamine biosynthesis. Expression of arginine decarboxylase (ADC), S-adenosylmethionine decarboxylase (AdoMetDC), and methionine adenosyltransferase (MAT) was measured in well-watered or droughted Flega (drought susceptible) and Patones (drought resistant) plants treated with salicylate 100 µM (black bars) or with the biologically inactive isomer 4-hydroxybenzoic acid (4-hBA) (control, white bars). Oat GAPDH gene was used as an internal control to normalize gene expression. Data, expressed as fold change in expression of SA-treated plants with respect to controls (4-hBA-treated plants), are mean of at least three independent biological plus three technical replications ± standard error. *, **, and *** indicate significant differences with respect to treatments at p < 0.05, 0.01, and 0.001, respectively.