Changes of lipids composition in different ontogenetic stages of Thecaphora frezii: expression of key enzymes for lipid biosynthetic pathways.

AIMS: It is known that Thecaphora frezii produces peanut smut that generates numerous economic losses. For this reason, it is a priority to search for control strategies. In this sense, we investigated the lipid profile of this pathogen, as possible antifungal targets, regarding polar lipid composition, fatty acid profile, and transcriptional regulation of genes involved in each stage of the development. METHOD AND RESULTS: Lipids from T. frezii teliospores, basidiospores, and hyphae were analyzed by HPLC/CAD and CG/FID. We found differences in the unsaturation levels as well as in the long-chain fatty acids along the stages. Phosphatidylcholine was the main component in the three development stages, followed by cardiolipins. Phosphatidylinositol, phosphatidylethanolamine, and lyso-phosphatidylethanolamine were found in similar amounts in all stages. Although ergosterol was not detected, we found two unsaponifiable lipids. In addition, we found transcripts that encode 28 enzymes involved in the biosynthesis of three lipids by RNA-Seq. CONCLUSIONS: Thecaphora frezii shows changes in the composition of membrane lipids in different ontogenetic stages as well as in the expression of transcripts for enzymes involved in lipid biosynthesis.

Phytotoxic activity in Flourensia campestris and isolation of (--)-hamanasic acid A as its active principle compound.

An aqueous extract from Flourensia campestris (Asteraceae) dry aerial parts showed strong inhibition on the germination and growth of Lactuca sativa. Based on bio-guided chromatographic fractionation of aq. extracts from dry and fresh leaves and spectroscopic means, (-)-hamanasic acid A (7-carboxy-8-hydroxy-1(2), 12(13)-dien-bisabolene (1)) was isolated as the most inhibitory active principle on germination (ECg(50)=2.9 mM) and on root (ECr(50)=1.5 mM)/shoot (ECs(50)=2.0 mM) growth. As measured by GC, and correlated with a simple designed 2D-TLC, compound 1 was distributed throughout the plant, with a remarkably high concentration (1.6%) in the leaves and the inflorescences. At least a quarter of the amount of 1 was found in aqueous extracts suggesting that leaching would be a key route for its release into the environment. By contrast, leaf essential oils (HD) between 0.5 and 1.5 µl ml(-1) did not show herbicidal effects and 1 was not found in them (TLC) nor among volatiles (HS-SPME). Volatile compositions were assessed by GC-FID and GC-MS and led to the identification of 23 compounds (4 monoterpenes and 19 sesquiterpenes) with a wide seasonal (spring-summer%) variation, represented principally by bicyclo-germacrene (37-6%), spathulenol (4-32%), globulol (20-0%), beta-caryophyllene (15-6%), caryophyllene oxide (1-13%) and bicycloelemene (10-1%), respectively. The high amount of 1 in F. campestris together with its feasibility of being extracted with water suggest that (-)-hamanasic acid A is an allelochemical in this species. Species-specific studies must be carried out to evaluate the potential of 1 as a natural herbicidal compound.

Screening of Argentinian plants for pesticide activity.

Aerial parts of 27 plant species native to Argentina were tested in anti-insect, germination inhibition and bactericide bio-assays. In antifeedant assays on Epilachna paenulata larvae, 11 species showed strong feeding deterrent effects (higher than 90% at 200 microg/cm(2)). Twelve plants strongly inhibited the germination of Avena sativa seeds, but only six inhibited Raphanus sativum germination at 10 mg/ml. Four plants showed complete growth inhibition of Escherichia coli at a concentration of 2 mg/ml.