Preventive and Curative Effects of Salicylic and Methyl Salicylic Acid Having Antifungal Potential against Monilinia laxa and the Development of Phenolic Response in Apple Peel

The effects of salicylic acid (SA) and one of its better-known derivatives-methyl salicylic acid (MeSA)-on the infection of apple fruits with the fungus Monilinia laxa, which causes brown rot, were investigated. Since research to date has focused on preventive effects, we also focused on the curative use of SA and MeSA. Curative use of SA and MeSA slowed the progression of the infection. In contrast, preventive use was generally unsuccessful. HPLC-MS was used to analyze the content of phenolic compounds in apple peels in healthy and boundary peel tissues around lesions. The boundary tissue around the lesions of untreated infected apple peel had up to 2.2-times higher content of total analyzed phenolics (TAPs) than that in the control. Flavanols, hydroxycinnamic acids and dihydrochalcones were also higher in the boundary tissue. During the curative treatment with salicylates, the ratio of TAP content between healthy and boundary tissue was lower (SA up to 1.2-times higher and MeSA up to 1.3-times higher content of TAPs in boundary compared to those in healthy tissue) at the expense of also increasing the content in healthy tissues. The results confirm that salicylates and infection with the fungus M. laxa cause an increased content of phenolic compounds. Curative use of salicylates has a greater potential than preventive use in infection control.

[Phenylpropanoid pathway in plants and its role in response to heavy metal stress: a review]

Phenylpropanoid metabolic pathway is one of the most important secondary metabolic pathways in plants. It directly or indirectly plays an antioxidant role in plant resistance to heavy metal stress, and can improve the absorption and stress tolerance of plants to heavy metal ions. In this paper, the core reactions and key enzymes of the phenylpropanoid metabolic pathway were summarized, and the biosynthetic processes of key metabolites such as lignin, flavonoids and proanthocyanidins and relevant mechanisms were analyzed. Based on this, the mechanisms of key products of phenylpropanoid metabolic pathway in response to heavy metal stress were discussed. The perspectives on the involvement of phenylpropanoid metabolism in plant defense against heavy metal stress provides a theoretical basis for improving the phytoremediation efficiency of heavy metal polluted environment.

Functional analysis of 4-coumarate: CoA ligase from Dryopteris fragrans in transgenic tobacco enhances lignin and flavonoids

4-Coumaric acid: coenzyme A ligase (4CL) is a key enzyme in the phenylpropanoid metabolic pathway that regulates the biosynthesis of lignin and flavonoids. Therefore, the study of 4CL is important to explore the accumulation and regulation of metabolites. This study investigated the role that the 4CL2 gene from Dryopteris fragrans (Df4CL2) plays in the metabolite synthesis. Changes in gene expression, enzyme activity, and the content of lignin and flavonoids were measured in different tissues of tobacco as model plant that was successfully transferred with Df4CL2. Tobacco plants with Df4CL2 (transgenic tobacco, TT) were successfully obtained via the Agrobacterium-transformation method. This TT tended to be thicker and had an earlier flowering period than wild type tobacco (WT). The expression levels of Df4CL2 were higher in the stem, leaf, and root in TT compared to WT. In addition, compared to WT, TT had higher 4CL enzyme activity and higher lignin and flavonoids contents. This suggests that Df4CL2 is involved in the synthesis of lignin and flavonoids in D. fragrans. This research provides important evidence toward understanding the phenylpropanoid metabolic pathway in ferns.