Screening of antimicrobial and insecticidal properties of essential oils extracted from three Tunisian aromatic and medicinal plants.

The essential oils (EOs) of Coriandrum sativum, Carum carvi and Artemisia herba-alba have been screened for their insecticidal activity against Tribolium castaneum, Sitophilus oryzae and Lasioderma serricorne and for their antimicrobial activity against Gram (+), Gram (-) bacteria and against yeast strain. Artemisia herba-alba EO showed good insecticidal activity with 24-h against L. serricorne (LC50 = 29.7) and against T. castaneum (66.1 µg/mL) and antibacterial potentials against Staphyloccocus aureus (MIC = 0.125 mg/mL). The antimicrobial activities of C. carvi EO, rich in D-carvone (72.4%) and D-limonene (23.8%) were particularly remarkable, with LC50 of 27.9 µg/mL against L. serricorne. Similarly, coriander EO, with linalool (64.6%) as the major compound was selected for its antimicrobial activities (Candida albicans, MIC = 1 mg/mL). These findings demonstrated that the tested EOs could be used as a natural source of insecticidal and antimicrobial activity, which may have a variety of uses in the food and pharmaceutical sectors.

Ethylene controls cambium stem cell activity via promoting local auxin biosynthesis.

The vascular cambium is the main secondary meristem in plants that produces secondary phloem (outside) and xylem (inside) on opposing sides of the cambium. The phytohormone ethylene has been implicated in vascular cambium activity, but the regulatory network underlying ethylene-mediated cambial activity remains to be elucidated. Here, we found that PETAL MOVEMENT-RELATED PROTEIN1 (RhPMP1), an ethylene-inducible HOMEODOMAIN-LEUCINE ZIPPER I transcription factor in woody plant rose (Rosa hybrida), regulates local auxin biosynthesis and auxin transport to maintain cambial activity. Knockdown of RhPMP1 resulted in smaller midveins and reduced auxin content, while RhPMP1 overexpression resulted in larger midveins and increased auxin levels compared with the wild-type plants. Furthermore, we revealed that Indole-3-pyruvate monooxygenase YUCCA 10 (RhYUC10) and Auxin transporter-like protein 2 (RhAUX2), encoding an auxin biosynthetic enzyme and an auxin influx carrier, respectively, are direct downstream targets of RhPMP1. In summary, our results suggest that ethylene promotes an auxin maximum in the cambium adjacent to the xylem to maintain cambial activity.