Metabolomic fingerprint of Mentha rotundifolia L. Leaf tissues promotes this species as a potential candidate for sustainable production of biologically active molecules.

Background The Mentha rotundifolia L. (Lamiaceae family), is a medicinal herb used since the ancient times as an antiseptic, analgesic and anti-inflammatory agent. In the present work, metabolomic profiling of two Mentha rotundifolia L. ecotypes leaf tissues spontaneously growing in the North of Tunisia was achieved. Methods Phenolic contents (TPC, TFC and TTC) were assessed using colorimetric methods. Metabolomic profiling of leaf tissues extracts was assessed based on Gas Chromatography-Mass Spectrometry (GC/MS) analysis. The antioxidant ability of M. rotundifolia extracts was achieved based on two test systems namely DPPH and FRAP assays. Antimicrobial activity against a set of Gram negative and Gram positive bacteria was estimated by measuring ID, MIC and MBC values. Results Fifty metabolites were identified as belonging mainly to phenolics, fatty acids, terpenes, steroids and aldehydes classes with qualitative and quantitative variability. Most of the identified compounds are reputed bioactive with potent antioxidant, antimicrobial and anti-inflammatory among others effects. To confirm these findings common in vitro biological activities were achieved. The investigated extracts showed significant antioxidant abilities based on both 1,1-diphenyl-2-picrylhydrazyl (DPPH) and Ferric reducing antioxidant potential (FRAP) assays. Furthermore, the extracts revealed promising antimicrobial ability against tested Gram+ and Gram- bacterial strains (ID: 12.5-14.5 mm, MIC: 3.125-25 (µg/mL), MBC: 6.25-100 (µg/mL)). Conclusions Based on our findings Mentha rotundifolia L. leaves extracts present a potential source of natural antioxidants and diverse bioactive compounds which could be used in green pharmacy, food preservation, alternative medicine and natural therapies.

Ethylene Response Factors (ERF) are differentially regulated by different abiotic stress types in tomato plants.

Plants are sessile organisms, hence to face environmental constrains they developed strategies that rely on the activation of stress-response genes under the control of specific transcription factors. The plant hormone ethylene mediates physiological, developmental and stress responses through the activation of Ethylene Response Factors (ERFs) which belong to a large multigene family of transcription factors. While an increasing number of studies supports the involvement of ERFs in abiotic stress responses, so far the specific role of ERF family members in different abiotic stress conditions remains unexplored. The present work investigates the expression profile of a set of ERFs, representative of different ERF types, in tomato plants subjected to cold, heat, salt, drought and flooding conditions. The study revealed that a group of ERFs is preferentially associated with cold and heat stress responses while another set is expressed in response to salt, water and flooding stresses. Transactivation assays indicated that ERFs can regulate the expression of abiotic stress genes regardless of whether or not they harbor conserved GCC or DRE cis-elements in their promoter region. The outcome of the study provides clue on which ERFs should be targeted when aiming to improve adaptation to a particular stress type.

Ethylene response factor Sl-ERF.B.3 is responsive to abiotic stresses and mediates salt and cold stress response regulation in tomato.

Sl-ERF.B.3 (Solanum lycopersicum ethylene response factor B.3) gene encodes for a tomato transcription factor of the ERF (ethylene responsive factor) family. Our results of real-time RT-PCR showed that Sl-ERF.B.3 is an abiotic stress responsive gene, which is induced by cold, heat, and flooding, but downregulated by salinity and drought. To get more insight into the role of Sl-ERF.B.3 in plant response to separate salinity and cold, a comparative study between wild type and two Sl-ERF.B.3 antisense transgenic tomato lines was achieved. Compared with wild type, Sl-ERF.B.3 antisense transgenic plants exhibited a salt stress dependent growth inhibition. This inhibition was significantly enhanced in shoots but reduced in roots, leading to an increased root to shoot ratio. Furthermore, the cold stress essay clearly revealed that introducing antisense Sl-ERF.B.3 in transgenic tomato plants reduces their cell injury and enhances their tolerance against 14 d of cold stress. All these results suggest that Sl-ERF.B.3 gene is involved in plant response to abiotic stresses and may play a role in the layout of stress symptoms under cold stress and in growth regulation under salinity.