Altered properties and structures of root exudate polysaccharides in a root hairless mutant of barley

Root exudates and rhizosheaths of attached soil are important features of growing roots. To elucidate factors involved in rhizosheath formation, wild-type (WT) barley (Hordeum vulgare L. cv. Pallas) and a root hairless mutant, bald root barley (brb), were investigated with a combination of physiological, biochemical, and immunochemical assays. When grown in soil, WT barley roots bound ∼5-fold more soil than brb per unit root length. High molecular weight (HMW) polysaccharide exudates of brb roots had less soil-binding capacity than those of WT root exudates. Carbohydrate and glycan monoclonal antibody analyses of HMW polysaccharide exudates indicated differing glycan profiles. Relative to WT plants, root exudates of brb had reduced signals for arabinogalactan-protein (AGP), extensin, and heteroxylan epitopes. In contrast, the root exudate of 2-week-old brb plants contained ∼25-fold more detectable xyloglucan epitope relative to WT. Root system immunoprints confirmed the higher levels of release of the xyloglucan epitope from brb root apices and root axes relative to WT. Epitope detection with anion-exchange chromatography indicated that the increased detection of xyloglucan in brb exudates was due to enhanced abundance of a neutral polymer. Conversely, brb root exudates contained decreased amounts of an acidic polymer, with soil-binding properties, containing the xyloglucan epitope and glycoprotein and heteroxylan epitopes relative to WT. We, therefore, propose that, in addition to physically structuring soil particles, root hairs facilitate rhizosheath formation by releasing a soil-binding polysaccharide complex.

The root exudate of a root hairless mutant of barley, relative to wild type, has an altered pattern of polysaccharide epitopes and lesser amounts of an acidic soil-binding polysaccharide complex.     

Crystallization and preliminary X-ray and optical spectroscopic characterization of the photochemical reaction center from Rhodobacter sphaeroides strain 2.4.1

The photochemical reaction center from Rhodobacter sphaeroides 2.4.1 has been crystallized. The crystals were obtained in a solution of beta-octylglucoside by the vapor diffusion technique using polyethylene glycol 4000 as the precipitant at 22 degrees C. The orthorhombic crystals (space group P2(1)2(1)2(1)) have cell constants a = 142.5 A, b = 136.1 A, c = 78.5 A, and diffract to 3.7 A. The crystals display pronounced linear dichroism in the carotenoid absorption spectral region.     

Arabinogalactan proteins in embryogenic and non-embryogenic callus cultures of Euphorbia pulcherrima

The arabinogalactan protein (AGP) fractions of embryogenic and non-embryogenic callus lines of Euphorbia pulcherrima Willd. ex. Klotzsch were analysed over a cultivation period of 9 weeks using the β -glucosyl Yariv reagent and an anti-AGP antibody (LM2). The amount of AGPs detected with the Yariv reagent increased in embryogenic cultures during the development of somatic embryos. The embryogenic and non-embryogenic callus contained different sets of AGPs characterized with the Yariv reagent and the LM2 monoclonal antibody. AGPs recognized by LM2 are localized primarily in the protodermal cells of globular somatic embryos. The development of somatic embryos of E. pulcherrima appears to be associated with the presence of particular AGPs.     

Root border cells take up and release glucose-C

BACKGROUND AND AIMS: Border cells are released from the root tips of many plant species, and can remain viable in the rhizosphere for 1 week. Whether border cells are capable of controlled glucose exchange with their environment was investigated. METHODS: Border cells were removed from Zea mays L. root tips, and immersed in (14)C-labelled D-glucose. In one experiment, the hexose transport inhibitor, phlorizin, was used to investigate active glucose uptake from a range of glucose concentrations. In another experiment, glucose efflux from border cells was monitored over time. KEY RESULTS: Glucose uptake by the border cells increased with increasing glucose concentration from 0.2 to 20 mm. At 0.2 mm glucose, uptake was mainly active, as evidenced by the approx. 60 % inhibition with phlorizin. At 2 and 20 mm glucose, however, uptake was mainly via diffusion, as phlorizin inhibition was negligible. Glucose efflux increased with time for live border cells in both 2 and 20 mm glucose. There was no clear efflux/time pattern for heat-killed border cells. CONCLUSIONS: Border cells actively take up glucose, and also release it. Under our experimental conditions, glucose uptake and efflux were of similar order of magnitude. In the rhizosphere net glucose exchange will almost certainly depend on local soil conditions.     

The Benzidine Staining Method for Blood Vessels

Two modifications of the method are described: A. Living specimens of sabellid and serpluid polychaetes, earthworms, small tadpoles, or fish larvae are immersed in an approximately saturated solution of benzidine for 30 minutes and then 3% hydrogen peroxide is added until bubbles of gas appear. When the blood vessels appear dark blue, the specimens are fixed in acidified 70% alcohol, dehydrated, cleared and either mounted in Canada balsam as whole mounts, or embedded in paraffin, sectioned at 100 to 250µ and mounted. B. Material fixed in 10% formalin in sea-water, or in formalin hypertonic saline, is incubated at 37°C. for one hour in an aqueous mixture containing sodium nitroprusside, 0.1%; benzidine, acetic acid 0.5%, followed by a weak (0.01-0.02%) hydrogen peroxide solution for a further hour, embedded in paraffin, cut into thick sections and mounted.     

Effect of PG600 and adjusted mating times on reproductive performance in weaned sows

The administration of PG600 to sows at weaning induces >90% of sows to return to estrus within a week, but farrowing rate and litter size are often not improved. This study evaluated the effects of adjusted artificial insemination (AI) times based on weaning to estrus interval (WEI) and estrus to ovulation interval (EOI) following PG600. All sows were given PG600 at weaning and allotted to adjusted (ADJ, n=47) or non-adjusted (NA, n=46) mating times after the onset of estrus. Adjusted mating involved: (1) 2-3 days WEI, AI at 36 h and 48 h; (2) 4 days WEI, AI at 24h and 36 h; (3) 5 days WEI, AI at 12h and 24h; and (4) 6-7 days WEI, AI at 0 h and 12h. Mating for NA occurred at 0 h and 24h after onset of estrus. There was no effect of treatment on return to estrus (92.9% versus 92.5%) or ovulation (92.7% versus 92.5% for ADJ and NA, respectively). The proportion of first AI occurring within 24h prior to ovulation was increased (83.8% versus 50.0%) and closer to ovulation for ADJ compared to NA treatment (19.4h versus 27.3h, P<0.05). Treatment did not influence (P>0.10) the proportion of second AI occurring within 24h of ovulation (72.8% versus 56.6%) but did influence (P<0.05) the interval from second AI to ovulation for ADJ compared to NA (10.6h versus 3.3h). The ADJ treatment increased (P<0.05) the proportion of sows that received an AI within 24h before ovulation (98.8% versus 87.0%). However, treatment did not influence pregnancy (87.4%) or farrowing (79.5%) rates but the NA treatment tended to increase (P<0.10) total number of pigs born (11.8 versus 8.9). In conclusion, while AI times for ADJ appeared to occur within optimal periods, farrowing rates were not improved and litter size decreased, suggesting that two AI at 12h intervals and closer to the time of ovulation may be detrimental. Overall, these data suggest that for sows injected with PG600 at weaning and receiving two AI, breeding at 0 h and 24h after onset of estrus is recommended.