Expression of arabinogalactan proteins involved in Taxol production by immobilized Taxus cuspidata cells

Comparison of the Formation of Plant-Microbial Interface in Pisum sativum L. and Medicago truncatula Gaertn. Nitrogen-Fixing Nodules

Different components of the symbiotic interface play an important role in providing positional information during rhizobial infection and nodule development: successive changes in cell morphology correspond to subsequent changes in the molecular architecture of the apoplast and the associated surface structures. The localisation and distribution of pectins, xyloglucans, and cell wall proteins in symbiotic nodules of Pisum sativum and Medicago truncatula were studied using immunofluorescence and immunogold analysis in wild-type and ineffective mutant nodules. As a result, the ontogenetic changes in the symbiotic interface in the nodules of both species were described. Some differences in the patterns of distribution of cell wall polysaccharides and proteins between wild-type and mutant nodules can be explained by the activation of defence reaction or premature senescence in mutants. The absence of fucosylated xyloglucan in the cell walls in the P. sativum nodules, as well as its predominant accumulation in the cell walls of uninfected cells in the M. truncatula nodules, and the presence of the rhamnogalacturonan I (unbranched) backbone in meristematic cells in P. sativum can be attributed to the most striking species-specific features of the symbiotic interface.

Ultrasonic Extraction and Separation of Taxanes from Taxus cuspidata Optimized by Response Surface Methodology

Taxanes are natural compounds with strong antitumor activity. In this study, we first extracted taxanes from the needles of Taxus cuspidata using ultrasonic (US) extraction, and then assessed the effects of different extraction conditions on the yields of eight target compounds. Response surface methodology (RSM) was further used to optimize the extraction conditions: when the liquid-to-solid ratio was 20.88 times, ultrasonic power was 140.00 W, ultrasonic time was 47.63 min, and ethanol content in solvent was 83.50%, taxane yields reached the maximum value of 354.28 μg/g. Under these conditions, the actual extraction rate of taxanes from the needles was 342.27 μg/g. The scanning electron microscopy (SEM) results indicated that the morphology of the needles, suspension cells, and callus of Taxus cuspidata extracted by ultrasonic wave had changed, the pores of the sections of the needles extracted by ultrasonic wave had become relatively loose, and the pore diameter had obviously increased. The callus and overall structure of the suspension cells extracted by ultrasonic wave were destroyed, forming cell fragments. The components of Taxus cuspidata are complex; the high-performance liquid chromatography (HPLC) method established in this paper is suitable for the rapid and effective separation of taxanes in Taxus cuspidata. We systematically and comprehensively compared the yields of taxanes in needles, callus, and suspension cells of Taxus cuspidata, and the taxane yields were increased by the suspension cell culture.

Arabinogalactan-proteins from non-coniferous gymnosperms have unusual structural features

Arabinogalactan-proteins (AGPs), important signalling molecules of the plant cell wall, are structurally extensively investigated in angiosperms, but information on AGPs in gymnosperms is still limited. We characterized AGPs from the gymnosperms Ginkgo biloba, Ephedra distachya, Encephalartos longifolius and Cycas revoluta. The protein contents are comparable to that of angiosperm AGPs. Hydroxyproline is the site of linking the carbohydrate part and was detected in all AGPs with highest concentration in Cycas AGP (1.1 % of the AGP). Interestingly, with the exception of Cycas, all AGPs contained the monosaccharide 3-O-methylrhamnose not present in angiosperm polysaccharides. The carbohydrate moieties of Cycas and Ephredra showed the main components 1,3,6-linked galactose and terminal arabinose typical of angiosperm AGPs, whereas that of Ginkgo AGP was unique with 1,4-linked galactose as dominant structural element. Bioinformatic search for glycosyltransferases in Ginkgo genome also revealed a lower number of galactosyltransferases responsible for biosynthesis of the 1,3-Gal/1,6-Gal AGP backbone.

Spatial-temporal distribution of nitric oxide involved in regulation of phenylalanine ammonialyase activation and Taxol production in immobilized Taxus cuspidata cells

The generation of nitric oxide (NO) in Taxus cuspidata in immobilized support matrices and the potential role of NO as signal molecular in regulation of Taxol production were investigated. It was found that the immobilization induced a spatial and temporal-dependent NO burst in immobilized supported matrices. NO level reached the maximum in the central zone of immobilized supported matrices on day 20, which was more than twice compared with that in suspended cells. Further investigations showed that the phenylalanine ammonialyase (PAL) activity and Taxol production of the 20-day-old immobilized T. cuspidata cells increased by onefold and 11% after 4h treatment with 20 microM NO donor (sodium nitroprusside), respectively. NO inhibitor N(omega)-nitro-L-arginine and NO scavenger 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxyde partially blocked PAL activity and Taxol accumulation in immobilized cells. These results suggest that NO plays a signal role in regulation of PAL activity and Taxol production in immobilized T. cuspidata cells.