Aucsia gene silencing causes parthenocarpic fruit development in tomato.

In angiosperms, auxin phytohormones play a crucial regulatory role in fruit initiation. The expression of auxin biosynthesis genes in ovules and placenta results in uncoupling of tomato (Solanum lycopersicum) fruit development from fertilization with production of parthenocarpic fruits. We have identified two newly described genes, named Aucsia genes, which are differentially expressed in auxin-synthesis (DefH9-iaaM) parthenocarpic tomato flower buds. The two tomato Aucsia genes encode 53-amino-acid-long peptides. We show, by RNA interference-mediated gene suppression, that Aucsia genes are involved in both reproductive and vegetative plant development. Aucsia-silenced tomato plants exhibited auxin-related phenotypes such as parthenocarpic fruit development, leaf fusions, and reflexed leaves. Auxin-induced rhizogenesis in cotyledon explants and polar auxin transport in roots were reduced in Aucsia-silenced plants compared with wild-type plants. In addition, Aucsia-silenced plants showed an increased sensitivity to 1-naphthylphthalamic acid, an inhibitor of polar auxin transport. We further prove that total indole-3-acetic acid content was increased in preanthesis Aucsia-silenced flower buds. Thus, the data presented demonstrate that Aucsia genes encode a novel family of plant peptides that control fruit initiation and affect other auxin-related biological processes in tomato. Aucsia homologous genes are present in both chlorophytes and streptophytes, and the encoded peptides are distinguished by a 16-amino-acid-long (PYSGXSTLALVARXSA) AUCSIA motif, a lysine-rich carboxyl-terminal region, and a conserved tyrosine-based endocytic sorting motif.

Changes in the tobacco leaf apoplast proteome in response to salt stress.

The apoplast of plant cells is a dynamic compartment involved in many processes, including maintenance of tissue shape, development, nutrition, signalling, detoxification and defence. In this work we used Nicotiana tabacum plants as a model to investigate changes in the soluble apoplast composition induced in response to salt stress. Apoplastic fluid was extracted from leaves of control plants and plants exposed to salt stress, using a vacuum infiltration procedure. Two-dimension electrophoretic analyses revealed about 150 polypeptide spots in the pH range of 3.0 to 10.0, in independent protein extracts, with a high level of reproducibility between the two sample sets. Quantitative evaluation and statistical analyses of the resolved spots in treated and untreated samples revealed 20 polypeptides whose abundance changed in response to salt stress. Mass spectroscopic peptide separation and sequencing was used to identify polypeptides affected by salt stress. While the levels of some proteins were reduced by salt-treatment, an enhanced accumulation of protein species known to be induced by biotic and abiotic stresses was observed. In particular, two chitinases and a germin-like protein increased significantly and two lipid transfer proteins were expressed entirely de novo. Some apoplastic polypeptides, involved in cell wall modifications during plant development, remained largely unchanged. The significance of these components is discussed in the context of stress responses in plants.

The alpha' subunit from soybean 7S globulin lowers plasma lipids and upregulates liver beta-VLDL receptors in rats fed a hypercholesterolemic diet.

Recent data concerning the effect of soybean 7S globulin subunits on the upregulation of LDL receptors in Hep G2 cells identified the alpha' subunit as the candidate responsible for this biological effect. In vivo evaluation of this subunit on cholesterol homeostasis was hampered by the lack of suitable amounts of alpha' chain. A novel separation procedure allowed us to investigate the effects of alpha' subunit administration on plasma cholesterol and triglyceride levels, as well as on the activity of liver beta-VLDL receptors of rats fed a hypercholesterolemic (HC) diet. Rats were divided into 9 groups fed the following diets for 28 d: standard diet; HC diet; HC diets + 5, 10, and 20 mg/(kg body weight. d) of alpha' subunit; HC diets + 50, 100, and 200 mg/(kg body weight. d) of soybean 7S globulin; HC diet + 200 mg/(kg body weight. d) clofibrate. The highest dose of the alpha' subunit decreased plasma cholesterol and triglycerides 36 and 34%, respectively, in rats fed the HC diet; 10-fold amounts clofibrate reduced plasma cholesterol and triglycerides 38 and 41%. The activity of liver beta-VLDL receptors of rats fed the HC diet with the highest dose of the alpha' subunit had a 96% increase in binding compared with the HC diet group, thus restoring the receptor activity to that of rats fed the standard diet. These results represent the first in vivo evidence of both the plasma lipid-lowering properties and the upregulation of liver beta-VLDL receptors induced by the soybean alpha' subunit.