Effect of high frequency ultrasound pre-treatment on nutritional and technological properties of tomato paste.

This study investigates the separate effect of sonication (US, carried out for 5 and 15 min) and thermal treatment (90 °C for 5 min) on nutritional and technological properties of tomato paste. US treatments did not affect the colour parameters and decreased the level of total acidity. Ascorbic acid content was slightly reduced after 5 min US but halved by pasteurization, while total carotenoids (TCC) and lycopene (LC) decreased in non-pasteurized samples after 15 min US. Neither the TCC nor the LC significantly changed in US-pasteurized samples if compared to controls. Microscopic analyses suggested a possible increased bioaccessibility of lycopene in US treated samples due to an enhancement of free lycopene clusters. Viscosity decreased as a consequence of thermal stress, although sonication contributed as well. The present findings suggest that 5 min sonication before pasteurization can enhance the nutritional characteristics of tomato paste, besides improving its texture.

Lepidium meyenii (Maca) does not exert direct androgenic activities.

Maca is the edible root of the Peruvian plant Lepidum meyenii, traditionally employed for its purported aphrodisiac and fertility-enhancing properties. This study aimed at testing the hypothesis that Maca contains testosterone-like compounds, able to bind the human androgen receptor and promote transcription pathways regulated by steroid hormone signaling. Maca extracts (obtained with different solvents: methanol, ethanol, hexane and chloroform) are not able to regulate GRE (glucocorticoid response element) activation. Further experiments are needed to assess which compound, of the several Maca's components, is responsible of the observed in vivo effects.

Misfolding and aggregation of vacuolar glycoproteins in plant cells.

Phaseolin and lectin-related polypeptides, the abundant oligomeric glycoproteins of bean seeds, are synthesized on the endoplasmic reticulum (ER) and then transported to the storage vacuole via the Golgi apparatus. Glycosylation and folding are among the major modifications these proteins undergo in the ER. Although a recurrent role of N-glycosylation is on protein folding, in previous studies on common bean (Phaseolus vulgaris) seeds we demonstrated that the oligosaccharide side-chains are not required for folding, intracellular transport and activity of storage glycoproteins. We show here that in lima bean (Phaseolus lunatus), incubation of the developing cotyledon with tunicamycin to prevent glycosylation has a dramatic effect on the intracellular transport of the storage glycoproteins. When lacking their glycans, phaseolin and lectin-related polypeptides misfold and are retained in the ER as mixed aggregates to which the chaperone BiP irreversibly associates. The lumen of the ER becomes enlarged to accommodate the aggregated polypeptides. Intracellular transport of legumin, a naturally unglycosylated storage protein, is mostly unaffected by the inhibitor, indicating that the observed phenomenon specifically occurs on glycoproteins. Furthermore, recombinant lima bean phaseolin synthesized in tobacco protoplasts is also correctly folded and matured in the presence of tunicamycin. To our knowledge, this is the first report that describes in detail the block of intracellular transport of vacuolar glycoproteins in plant cells due to aggregation following glycosylation inhibition.

Sorting of phaseolin to the vacuole is saturable and requires a short C-terminal peptide.

Phaseolin, one of the major legume proteins for human nutrition, is a trimeric glycoprotein of the 7S class that accumulates in the protein storage vacuoles of common bean. Phaseolin is cotranslationally introduced into the lumen of the endoplasmic reticulum; from there, it is transported through the Golgi complex to the storage vacuoles. Phaseolin is also transported to the vacuole in vegetative tissues of transgenic plants. By transient and permanent expression in tobacco leaf cells, we show here that vacuolar sorting of phaseolin is saturable and that saturation leads to Golgi-mediated secretion from the cell. A mutated phaseolin, in which the four C-terminal residues (Ala, Phe, Val, and Tyr) were deleted, efficiently formed trimers but was secreted entirely outside of the cells in transgenic tobacco leaves, indicating that the deleted sequence contains information necessary for interactions with the saturable vacuolar sorting machinery. In the apoplast, the secreted phaseolin remained intact; this is similar to what occurs to wild-type phaseolin in bean storage vacuoles, whereas in vegetative vacuoles of transgenic plants, the storage protein is fragmented.

Heat-induced synthesis and tunicamycin-sensitive secretion of the putative storage glycoprotein conglutin gamma from mature lupin seeds.

SDS/PAGE, immune blotting with specific antibodies and amino acid sequence analyses revealed that 90% of the protein released from Lupinus albus seeds incubated in water at 60 degrees C for about 3 h was conglutin gamma, a putative storage glycoprotein already present in the protein bodies of mature seeds. Incorporation of [14C]leucine into the protein demonstrated that conglutin gamma was newly synthesized during the treatment and the use of protein synthesis inhibitors ruled out the secretion of constitutive conglutin gamma. Synthesis and secretion took place only over a narrow temperature range, 57.5-62.5 degrees C, and in a short time interval, 135-180 min, of incubation of the seed. The amount of secreted conglutin gamma, i.e. 1 mg/seed, was about three times that present inside the treated or untreated seed. Secreted conglutin gamma contained covalently linked carbohydrate as well as the constitutive protein. Inhibition of the glycosylation by tunicamycin did not affect conglutin gamma synthesis, but prevented its secretion from the seed, as indicated by quantifying conglutin gamma remaining in the seed. An accumulation of the protein outside the protein bodies and at the cotyledonary cell periphery was shown in these samples by immunocytochemistry. Peptide mapping of the fragments obtained by incubation of constitutive and secreted conglutin gamma with trypsin and pepsin revealed no difference between the two proteins. Lupin seeds were still viable after the treatment. However no similarities between conglutin gamma and heat-shock proteins were observed either in the amino acid sequence or other molecular features.