Cyclic monoterpene mediated modulations ofArabidopsis thalianaphenotype

Abstract

Monoterpenes at high atmospheric concentrations are strong growth inhibitors in allelopathic interactions. Effects depend on dose, molecular structure of the monoterpene and on the species of the receiver plant. Stomata are among the first targets affected by camphor and menthol. Previously, it could be demonstrated that the compounds induce swelling of the protoplasts, prevent stomatal closure and enhance transpiration. In this study, we show that the block of stomatal closure is accompanied by changes to the cytoskeleton, which has a direct role in stomatal movements. Although MPK3 (MAP3 kinase) and ABF4 gene expressions are induced within six hours, stomatal closure is prevented. In contrast to ABF4, ABF2 (both transcription factors) is not induced. MPK3 and ABF4 both encode for proteins involved in the process of stomatal closure. The expression of PEPCase, an enzyme important for stomatal opening, is down regulated. The leaves develop stress symptoms, mirrored by transient changes in the expression profile of additional genes: lipoxygenase 2 (LOX2), CER5, CER6 (both important for wax production) and RD29B (an ABA inducible stress protein). Non-invasive methods showed a fast response of the plant to camphor fumigations both in a rapid decrease of the quantum yield and in the relative growth rate. Repeated exposures to the monoterpenes resulted finally in growth reduction and a stress related change in the phenotype. It is proposed that high concentrations or repeated exposure to monoterpenes led to irreversible damages, whereas low concentrations or short-term fumigations may have the potential to strengthen the plant fitness.

Phytotoxic Effects and Mechanism of Action of Essential Oils and Terpenoids

“…Induced an alteration of plant water status, enhancing excessive transpiration. In fact, it induced protoplasts swelling, blocked stomatal closure altering the cytoskeleton organization (it has a pivotal role in stomatal movements); downregulated the expression of PEPCase (enzyme with an important role during stomatal opening) [124] Cucumis sativus Increased the concentration of cytosolic free calcium ions (Ca 2+ ) [136] Table 2. Cont.…”

“…Altered the plant water status, induced oxidative stress and physical damages to the photosynthetic machinery; plants responded by accumulating metabolites (amino acids, sugars, anthocyanins, among others) and protein involved in oxidative stress defense [127] S-Carvone Solanum tuberosum Reduced the activity of the 3-hydroxy-3-methylglutaryl coenzyme A reductase without affecting its mRNA level [138] Camphor Allium cepa Inhibited mitosis and cell respiration [103,139] Arabidopsis thaliana Altered the cuticular waxes structure and enhance leaf transpiration causing water losses and cell dehydration [123] Arabidopsis thaliana Disrupted actin filaments and microtubules affecting cell division [124] 1,8-Cineole Avena fatua Inhibited mitochondrial respiration in isolated organelles [139] Allium cepa Inhibited mitosis in all its stages [81] Allium cepa Induced swelling of the root tips, phenomenon known to be caused by an alteration of the cortical microtubules [103] 1,4-Cineole Allium cepa Inhibited the prophase of mitosis and induced malformations in the shoot, which was characterized by corkscrew-shape (handedness). [81] Echinochloa crus-galli, Cassia obtusifolia…”

Chloroplast signaling within, between and beyond cells

“…Indeed, strong membrane depolarization as well as calcium influx were observed upon treatment of tomato plants with GLVs, two phenomena often associated with a signal transduction cascade in other systems ( Zebelo et al, 2012 ). Rearrangements of cytoskeleton and expression of selected genes encoding, among others, protein kinases and transcription factors as well as changes in stomatal aperture were observed upon treatment with the monoterpenes camphor and menthol ( Kriegs et al, 2010 ). However, the concentrations used in the assay are inconsistent with physiological levels, thus the observed effects are questionable.…”

Cellular Base of Mint Allelopathy: Menthone Affects Plant Microtubules

“…Components from Eucalyptus essential oil, such as eucalyptol, aand b-pinene, camphene and camphor were reported to inhibit cell proliferation in roots by interfering with DNA synthesis in organelles and nucleus of the Brassica campestris root meristem (Nishida et al, 2005). Monoterpenes (camphor and menthol) have been found to affect stomatal opening through cytoskeletal changes as a response to the monoterpenes and have effects on the growth of Arabidopsis thaliana seedlings (Kriegs et al, 2010). Similarly, citral was found to be a strong inhibitor of seed germination in Triticum sativum, Amaranthus palmeri and Brassica nigra (Dudai et al, 1999).…”