Short-Term Effects of Trans-Cinnamic Acid on the Metabolism of Zea mays L. Roots

Abstract

trans-Cinnamic acid is a phenolic compound widely studied in plant metabolism due to its importance in regulating different plant processes. Previous studies on maize plants showed that this compound could affect plant growth and causes metabolic changes in the leaves when applied. However, its effects on root metabolism are not well known. This study analyses the short-term effect of trans-cinnamic acid on the morphology of vascular bundle elements and metabolism in maize roots. At short times (between 6 and 12 h), there is a reduction in the content of many amino acids which may be associated with the altered nitrogen uptake observed in earlier work. In addition, the compound caused an alteration of the vascular bundles at 48 h and seemed to have changed the metabolism in roots to favor lignin and galactose synthesis. The results obtained complement those previously carried out on maize plants, demonstrating that in the short term trans-cinnamic acid can trigger stress-coping processes in the treated plants.

Keywords: lignin; maize; metabolomics; root; stress; trans-cinnamic acid.

Figure 1

(a) Diameter of the vascular bundle after 48 h of treatment with trans-cinnamic acid expressed as a percentage with respect to the control. (b) Xylematic area after 48 h of treatment with trans-cinnamic acid expressed as percentage respect to the control. (c) Cross section of a maize control root. (d) Cross section of a maize trans-cinnamic treated root. (X), xylem; (Ph), phloem; (Pc); pericycle. (*) Indicates significant differences compared to the control (* p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001). Scales bars = 50 μm. Data were analysed with a t-test at p ≤ 0.05.

Figure 2

(a) Unsupervised PCA of the metabolomic changes on maize roots after 48 h treatment with 103 μM of trans−cinnamic acid. (b) Multivariate (PLS−DA) analysis of the metabolomic changes on maize roots after 48 h treatment with 103 μM of trans−cinnamic acid. (c) Important features identified by PLS−DA. The coloured boxes on the right indicate the relative concentrations of the corresponding metabolite in each group under study Times (T0 = 0 h; T1 = 6 h; T2 = 12 h; T3 = 24 h; T4 = 48 h). The treatments used were 0 μM (control, CT), and (treatment, T). N = 3.

Figure 3

Clustering result shown as heatmap (distance measure using Euclidean, and clustering algorithm using Ward method) of all the metabolites identified in seedlings exposed to trans-cinnamic acid compared to control. Each square represents the effect of trans−cinnamic acid on the amount of each metabolite using a false−colour scale. Red or blue regions indicate increased or decreased metabolite content, respectively. Times (T0 = 0 h; T1 = 6 h; T2 = 12 h; T3 = 24 h; T4 = 48 h). The treatments used were 0 μM (control, CT), and 103 μM (treatment, T) N = 3.