Metabolic engineering of cottonseed oil biosynthesis pathway via RNA interference.

Cottonseed oil is recognized as an important oil in food industry for its unique characters: low flavor reversion and the high level of antioxidants (VitaminE) as well as unsaturated fatty acid. However, the cottonseed oil content of cultivated cotton (Gossypium hirsutum) is only around 20%. In this study, we modified the accumulation of oils by the down-regulation of phosphoenolpyruvate carboxylase 1 (GhPEPC1) via RNA interference in transgenic cotton plants. The qRT-PCR and enzyme activity assay revealed that the transcription and expression of GhPEPC1 was dramatically down-regulated in transgenic lines. Consequently, the cottonseed oil content in several transgenic lines showed a significant (P < 0.01) increase (up to 16.7%) without obvious phenotypic changes under filed condition when compared to the control plants. In order to elucidate the molecular mechanism of GhPEPC1 in the regulation of seed oil content, we quantified the expression of the carbon metabolism related genes of transgenic GhPEPC1 RNAi lines by transcriptome analysis. This analysis revealed the decrease of GhPEPC1 expression led to the increase expression of triacylglycerol biosynthesis-related genes, which eventually contributed to the lipid biosynthesis in cotton. This result provides a valuable information for cottonseed oil biosynthesis pathway and shows the potential of creating high cottonseed oil germplasm by RNAi strategy for cotton breeding.

Bioconversion of apple pomace into a multienzyme bio-feed by two mixed strains of Aspergillus niger in solid state fermentation

Apple pomace is a wasted resource produced in large quantities and its deposit has caused serious environmental problems, so it is significance to make the full utilization of the residues. The objectives of this work were to produce multienzyme bio-feed, biodegrade the anti-nutritional factors such as pectin and tannins in apple pomace, and obtain the nutritional enrichment of the fermented substrate. The mixture of apple pomace and cottonseed powder (1:1, w/w), supplemented with 1 percent (w/w) (NH4)2SO4 and 0.1 percent (w/w) KH2PO4, was proved to be the optimum medium for the mixed strains of Aspergillus niger M2 and M3 (2:1, w/w). The activities of pectinase, proteinase and cellulase achieved 21168 u/g, 3585 u/g and 1208u/g, and the biodegradation rates of pectin and tannins reached 99.0 percent and 66.1 percent, respectively, when 0.4 percent(w/w) of the test fungiwere inoculated and incubated at 30ºC for 48 hrs in solid state fermentation. The utilization of apple pomace in the paper can be served as a model for the similar waste recycling.