The double knockdown of the mitochondrial uncoupling protein isoforms reveals partial redundant roles during Arabidopsis thaliana vegetative and reproductive development.

Mitochondrial uncoupling proteins (UCPs) are specialized proteins capable of dissipating the proton electrochemical gradient generated in respiration independent of ATP synthesis. Three UCP coding genes with distinct expression patterns have been identified in Arabidopsis thaliana (namely UCP1, UCP2 and UCP3). Here, we generated T-DNA double-insertion mutants (ucp1 ucp2, ucp1 ucp3 and ucp2 ucp3) to investigate the functionality of the Arabidopsis UCP isoforms. A strong compensatory effect of the wild-type UCP gene was found in the double-knockdown lines. Higher levels of reactive oxygen species (ROS) were observed in vegetative and reproductive organs of double mutant plants. This exacerbated oxidative stress in plants also increased lipid peroxidation but was not compensated by the activation of the antioxidant system. Alterations in O2 consumption and ADP/ATP ratio were also observed, suggesting a change in mitochondrial energy-generating processes. Deficiencies in double-mutants were not limited to mitochondria and also changed photosynthetic efficiency and redox state. Our results indicate that UCP2 and UCP3 have complementary function with UCP1 in plant reproductive and vegetative organ/tissues, as well as in stress adaptation. The partial redundancy between the UCP isoforms suggests that they could act separately or jointly on mitochondrial homeostasis during A. thaliana development.

Chemical constituents and allelopathic activity of Machaerium eriocarpum Benth.

The analysis by HPLC-PDA of the hydroalcoholic extract of the leaves of M. eriocarpum together with the injection of the fractions containing the already identified metabolites allowed the detection of at least 5 flavonoids, of which two are derived from apigenin and three from luteolin. After isolating larger amounts of isovitexin (I), assays were performed to evaluate the allelopathic activity together with the crude extract. The results show that the initial inhibition indexes were very similar to those observed in the treatments with F17 (Fraction enriched in isovitexin) and F18 (isovitexin), mainly in the concentrations of 500 and 1000 mg L-1. The index of the number of lateral roots, an increase of the inhibitory effect is observed with the increase of the concentration of M. eriocarpum extract.

Chemical composition of essential oils from the vegetative and reproductive structures of Copaifera langsdorffii Desf.

GC/FID and GC-MS analysis revealed germacrene D, bicyclogermacrene, α-cadinol and cubenol as major compounds from aril. Germacrene D, bicyclogermacrene, trans-caryophyllene and δ-elemene are major compounds in fruits. Germacrene D, spathulenol, trans-caryophyllene and caryophyllene oxide are major compounds in leaves. Furthermore, multivariate analysis revealed distinct groups between the composition of essential oils from aril and fruit, when compared with terpene production found in leaves. Lipid composition found in arils could be protected by the presence of non-oxygenated sesquiterpenes, as germacrene D and bicyclogermacrene. Chemical profiles of essential oils from the fruits, arils and leaves of Copaifera langsdorffii Desf. revealed different compositions, which could be related to environmental pressures. Thereby, non-oxygenated sesquiterpenes can also work against herbivory, pathogens and predator's attack, emphasising the importance of further studies among terpenes, ecology interactions and plant physiology.

Phytotoxic activities of Mediterranean essential oils.

Twelve essential oils from Mediterranean aromatic plants were tested for their phytotoxic activity, at different doses, against the germination and the initial radicle growth of seeds of Raphanus sativus, Lactuca sativa and Lepidium sativum. The essential oils were obtained from Hyssopus officinalis, Lavandula angustifolia, Majorana hortensis, Melissa officinalis, Ocimum basilicum, Origanum vulgare, Salvia officinalis and Thymus vulgaris (Lamiaceae), Verbena officinalis (Verbenaceae), Pimpinella anisum, Foeniculum vulgare and Carum carvi (Apiaceae). The germination and radicle growth of tested seeds were affected in different ways by the oils. Thyme, balm, vervain and caraway essential oils were more active against both germination and radicle elongation.