Proline metabolic dynamics and its implication in the drought tolerance of peanut plants

FURLAN, A., BIANUCCI, E.; GIORDANO, W.; CASTRO, S.; BECKER, D.

Salta

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB Congress; 2019

Proline metabolism and turnover, rather than just proline accumulation, contributes positively in multiple ways in plant tolerance. However, under some circumstances, reactive oxygen species generated as a by-product of the catabolism of proline is responsible for oxidative damage. In order to understand the response of proline metabolism and its implication in the drought-tolerance of peanut plants, transcriptional and biochemical analyses were performed during water stress in two peanut cultivars with contrasting tolerance to drought stress (Granoleico and EC-98). To exacerbate and help identify plant responses, the amino acid proline and its analogue, thiazolidine-4-carboxylic acid (T4C), which are substrates of a proline catabolic enzyme, were added exogenously to water stressed plants. Upon exposure to polyethylene glycol (PEG), peanut plant leaves from both cultivars had significantly lower relative water content and accumulated proline; only plants from the drought sensitive cultivar, Granoleico, exhibited oxidative damage (thiobarbituric acid reactive substances (TBARs) accumulation). Pre-treatment with exogenous proline or its analogue gave a contrasting response: proline and hydrogen peroxide accumulation and TBARs reduction. Both cultivars showed increased proline biosynthesis genes expression (P5CS1, P5CS2a, P5CS2b, P5CR) when exposed to water stress, but showed opposite responses in the relative expression of proline catabolism genes (ProDH1, ProDH2), which increased only in the sensitive cultivar. The drought tolerant EC-98 cultivar exhibited unique changes when pretreated with T4C, with mRNA levels of genes coding for proline biosynthesis (the four analyzed) and catabolism (P5CDH), significantly up-regulated even in the absence of water stress. Thus, higher proline metabolism in the drought tolerant cultivar, EC-98, relative to the sensitive cultivar (Granoleico), may contribute to the tolerant phenotype. Finally, T4C may be a potentially useful protecting agent in drought stress conditions for specific cultivars.