Root exudate of pmi tomato mutant M161 reduces AM fungal proliferation in vitro

Soluble factors released from roots of the pre-mycorrhizal infection (pmi) myc(-) tomato mutant M161 were analyzed and compared with normal wild-type released factors. Aseptic whole exudates from the M161 mutant retarded the proliferation of Glomus intraradices in vitro. When the whole exudate was further fractionated on a C18 SEPAK cartridge, the 50/70% methanol fraction showed an activity against hyphal tip growth of Gigaspora gigantea and Gl. intraradices. Preliminary characterization of the exudate suggests that the inhibitory moieties are heat labile, bind to PVPP (polyvinyl polypyrrolidone), and are not volatile. This is the first reported instance of the inhibition by a myc(-) plant being ascribed to inhibitory component(s) released in root exudate.     

The FEI2-SOS5 pathway and CELLULOSE SYNTHASE 5 are required for cellulose biosynthesis in the Arabidopsis seed coat and affect pectin mucilage structure

A common adaptation in angiosperms is the deposition of hydrophilic mucilage into the apoplast of seed coat epidermal cells during the course of their differentiation. Upon imbibition, seed mucilage, composed mainly of carbohydrates (i.e. pectins, hemicelluloses and glycans) expands rapidly, encapsulating the seed and aiding in seed dispersal and germination. The FEI1/FEI2 receptor-like kinases and the SOS5 extracellular GPI-anchored protein were previously shown to act on a pathway regulating cellulose biosynthesis during Arabidopsis root elongation. In the highlighted study, we demonstrated that FEI2 and SOS5 regulate the production of the cellulosic rays deposited across the inner adherent-layer of seed mucilage. Mutations in either fei2 or sos5 disrupted the formation of rays, which was associated with an increase in the soluble, outer layer of pectin mucilage and accompanied by a reduction in the inner adherent-layer. Mutations in CELLULOSE SYNTHASE 5 also led to reduced rays and mal-partitioning of the pectic component of seed mucilage, further establishing a structural role for cellulose in seed mucilage. Here, we show that FEI2 expressed from a CaMV 35S promoter complemented both root and seed mucilage defects of the fei1 fei2 double mutant. In contrast, expression of FEI1 from a 35S promoter complemented the root, but not the seed phenotype of the fei1 fei2 double mutant, suggesting that unlike in the root, FEI2 plays a unique and non-redundant role in the regulation of cellulose synthesis in seed mucilage. Altogether, these data suggest a novel role for cellulose in anchoring the pectic component of seed mucilage to the seed surface and indicate that the FEI2 protein has a function distinct from that of FEI1, despite the high sequence similarity of these RLKs.     

Oligonucleotide-assisted cleavage and ligation: a novel directional DNA cloning technology to capture cDNAs. Application in the construction of a human immune antibody phage-display library

The use of oligonucleotide-assisted cleavage and ligation (ONCL), a novel approach to the capture of gene repertoires, in the construction of a phage-display immune antibody library is described. ONCL begins with rapid amplification of cDNA ends to amplify all members equally. A single, specific cut near 5′ and/or 3′ end of each gene fragment (in single stranded form) is facilitated by hybridization with an appropriate oligonucleotide adapter. Directional cloning of targeted DNA is accomplished by ligation of a partially duplex DNA molecule (containing suitable restriction sites) and amplification with primers in constant regions. To demonstrate utility and reliability of ONCL, a human antibody repertoire was cloned from IgG mRNA extracted from human B-lymphocytes engrafted in Trimera mice. These mice were transplanted with peripheral blood lymphocytes from Candida albicans infected individuals and subsequently immunized with C.albicans glyceraldehyde-3-phosphate dehydrogenase (GAPDH). DNA sequencing showed that ONCL resulted in efficient capture of gene repertoires. Indeed, full representation of all V_H families/segments was observed showing that ONCL did not introduce cloning biases for or against any V_H family. We validated the efficiency of ONCL by creating a functional Fab phage-display library with a size of 3.3 × 10¹⁰ and by selecting five unique Fabs against GAPDH antigen.     

Antepartum Membrane Stripping in GBS Carriers,Is It Safe? (The STRIP-G Study)

Objective

Stripping of the membranes is an established and widely utilized obstetric procedure associated with higher spontaneous vaginal delivery rates, reduced need for formal induction of labor and a lower likelihood of post-term pregnancy. Due to the theoretical concern of bacterial seeding during the procedure many practitioners choose not to sweep the membranes in Group B Streptococcus (GBS) colonized patients. We conducted ‘the STRIP-G study’ in order to determine whether maternal and neonatal outcomes are affected by GBS carrier status in women undergoing membrane stripping.

Study design

We conducted a prospective study in a tertiary referral center, comparing maternal and neonatal outcomes following membrane stripping among GBS-positive, GBS-negative, and GBS-unknown patients. We compared the incidence of composite adverse neonatal outcomes (primary outcome) among the three study groups, while secondary outcome measure was composite adverse maternal outcomes.

Results

A total of 542 women were included in the study, of which 135 were GBS-positive, 361 GBS-negative, and 46 GBS-unknown status. Demographic, obstetric, and intra-partum characteristics were similar for all groups. Adverse neonatal outcomes were observed in 8 (5.9%), 31 (8.6%), and 2 (4.3%) in the GBS-positive, GBS-negative, and unknown groups, respectively (P = 0.530), (Odds Ratio between GBS-Positive vs. GBS-Negative groups 0.67 (95%, CI = 0.30–1.50)); while composite adverse maternal outcomes occurred in 9 (6.66%), 31 (8.59%), and 5 (10.87%) in the GBS-positive, GBS-negative, and unknown groups, respectively (P = 0.617).

Conclusions

Antepartum membrane stripping in GBS carriers appears to be a safe obstetrical procedure that does not adversely affect maternal or neonatal outcomes.     

Strigolactones interact with ethylene and auxin in regulating root-hair elongation in Arabidopsis

Strigolactones (SLs) or derivatives thereof have been identified as phytohormones, and shown to act as long-distance shoot-branching inhibitors. In Arabidopsis roots, SLs have been suggested to have a positive effect on root-hair (RH) elongation, mediated via the MAX2 F-box. Two other phytohormones, auxin and ethylene, have been shown to have positive effects on RH elongation. Hence, in the present work, Arabidopsis RH elongation was used as a bioassay to determine epistatic relations between SLs, auxin, and ethylene. Analysis of the effect of hormonal treatments on RH elongation in the wild type and hormone-signalling mutants suggested that SLs and ethylene regulate RH elongation via a common regulatory pathway, in which ethylene is epistatic to SLs, whereas the effect of SLs on RH elongation requires ethylene synthesis. SL signalling was not needed for the auxin response, whereas auxin signalling was not necessary, but enhanced RH response to SLs, suggesting that the SL and auxin hormonal pathways converge for regulation of RH elongation. The ethylene pathway requirement for the RH response to SLs suggests that ethylene forms a cross-talk junction between the SL and auxin pathways.     

Strigolactones affect lateral root formation and root-hair elongation in Arabidopsis

Strigolactones (SLs) have been proposed as a new group of plant hormones, inhibiting shoot branching, and as signaling molecules for plant interactions. Here, we present evidence for effects of SLs on root development. The analysis of mutants flawed in SLs synthesis or signaling suggested that the absence of SLs enhances lateral root formation. In accordance, roots grown in the presence of GR24, a synthetic bioactive SL, showed reduced number of lateral roots in WT and in max3-11 and max4-1 mutants, deficient in SL synthesis. The GR24-induced reduction in lateral roots was not apparent in the SL signaling mutant max2-1. Moreover, GR24 led to increased root-hair length in WT and in max3-11 and max4-1 mutants, but not in max2-1. SLs effect on lateral root formation and root-hair elongation may suggest a role for SLs in the regulation of root development; perhaps, as a response to growth conditions.