A cytosolic acyltransferase contributes to triacylglycerol synthesis in sucrose-rescued Arabidopsis seed oil catabolism mutants.

Triacylglycerol (TAG) levels and oil bodies persist in sucrose (Suc)-rescued Arabidopsis (Arabidopsis thaliana) seedlings disrupted in seed oil catabolism. This study set out to establish if TAG levels persist as a metabolically inert pool when downstream catabolism is disrupted, or if other mechanisms, such as fatty acid (FA) recycling into TAG are operating. We show that TAG composition changes significantly in Suc-rescued seedlings compared with that found in dry seeds, with 18:2 and 18:3 accumulating. However, 20:1 FA is not efficiently recycled back into TAG in young seedlings, instead partitioning into the membrane lipid fraction and diacylglycerol. In the lipolysis mutant sugar dependent1and the ß-oxidation double mutant acx1acx2 (for acyl-Coenzyme A oxidase), levels of TAG actually increased in seedlings growing on Suc. We performed a transcriptomic study and identified up-regulation of an acyltransferase gene, DIACYLGLYCEROL ACYLTRANSFERASE3 (DGAT3), with homology to a peanut (Arachis hypogaea) cytosolic acyltransferase. The acyl-Coenzyme A substrate for this acyltransferase accumulates in mutants that are blocked in oil breakdown postlipolysis. Transient expression in Nicotiana benthamiana confirmed involvement in TAG synthesis and specificity toward 18:3 and 18:2 FAs. Double-mutant analysis with the peroxisomal ATP-binding cassette transporter mutant peroxisomal ABC transporter1 indicated involvement of DGAT3 in the partitioning of 18:3 into TAG in mutant seedlings growing on Suc. Fusion of the DGAT3 protein with green fluorescent protein confirmed localization to the cytosol of N. benthamiana. This work has demonstrated active recycling of 18:2 and 18:3 FAs into TAG when seed oil breakdown is blocked in a process involving a soluble cytosolic acyltransferase.

A Papaver somniferum 10-gene cluster for synthesis of the anticancer alkaloid noscapine.

Noscapine is an antitumor alkaloid from opium poppy that binds tubulin, arrests metaphase, and induces apoptosis in dividing human cells. Elucidation of the biosynthetic pathway will enable improvement in the commercial production of noscapine and related bioactive molecules. Transcriptomic analysis revealed the exclusive expression of 10 genes encoding five distinct enzyme classes in a high noscapine-producing poppy variety, HN1. Analysis of an F(2) mapping population indicated that these genes are tightly linked in HN1, and bacterial artificial chromosome sequencing confirmed that they exist as a complex gene cluster for plant alkaloids. Virus-induced gene silencing resulted in accumulation of pathway intermediates, allowing gene function to be linked to noscapine synthesis and a novel biosynthetic pathway to be proposed.

Factors limiting the synthesis of virgin olive oil volatile esters.

The aim of the present work was to establish the limiting factors affecting the biosynthesis of volatile esters present in virgin olive oil (VOO). Oil volatile fractions of the main Spanish olive cultivars, Arbequina and Picual, were analyzed. It was observed that acetate esters were the most abundant class of volatile esters in the oils, in concordance with the high content of acetyl-CoA found in olive fruit, and that the content of C6 alcohols is limited for the synthesis of volatile esters during the production of VOO. Thus, the increase of C6 alcohol availability during VOO production produced a significant increase of the corresponding ester in the oils in both cultivars at two different maturity stages. However, the increase of acetyl-CoA availability had no effect on the VOO volatile fraction. The low synthesis of these C6 alcohols seems not to be due to a shortage of precursors or cofactors for alcohol dehydrogenase (ADH) activity because their increase during VOO production had no effect on the C6 alcohol levels. The experimental findings are compatible with a deactivation of ADH activity during olive oil production in the cultivars under study. In this sense, a strong inhibition of olive ADH activity by compounds present in the different tissues of olive fruit has been observed.

Toxicological evaluation of an ethanolic extract from Chiococca alba roots.

The roots of Chiococca alba have been employed to treat rheumatic disorders and for other therapeutic purposes in Brazil and elsewhere. This study was undertaken to evaluate the toxicological properties of an ethanolic extract from Chiococca alba roots (EE), including mutagenicity in the Salmonella assay and acute and subacute toxicity to mice. Single oral doses of EE caused hypoactivity, but no deaths were noted up to the highest dose tested (2000 mg/kg). EE (500 mg/kg p.o.) reduced mouse locomotion in the open field test. EE was markedly more toxic when given by intraperitoneal (i.p.) and subcutaneous (s.c.) routes. Acute approximate lethal doses (ALD) were 125 mg/kg (males) and 250 mg/kg (females) and 250 mg/kg (both sexes) by i.p. and s.c. routes, respectively. Deaths after single doses were preceded by hypoactivity, ataxia and lethargy. Repeated administration of EE by gavage for 14 days caused no deaths. Activity of liver monooxygenases (pentoxy- and ethoxyresorufin-O-dealkylases) was not altered by repeated treatment with EE (2000 mg/kg/day p.o.). Administration of EE by the i.p. route for 14 days decreased weight gain and caused anemia, neutrophilia and deaths. The no-observed-adverse-effect level (NOAEL) for subacute treatment by the i.p. route was as low as 15.6 mg of EE/kg body weight (wt)/day. EE was not mutagenic in the Salmonella/microsome assay with TA100, TA98, TA97a and TA1535 strains. In summary, EE was not mutagenic and presented a low acute and subacute toxicity by the oral route. Toxicities by parenteral routes, however, were more pronounced.