Higher Plant Cytochrome b5 Polypeptides Modulate Fatty Acid Desaturation

BACKGROUND: Synthesis of polyunsaturated fatty acids (PUFAs) in the endoplasmic reticulum of plants typically involves the fatty acid desaturases FAD2 and FAD3, which use cytochrome b(5) (Cb5) as an electron donor. Higher plants are reported to have multiple isoforms of Cb5, in contrast to a single Cb5 in mammals and yeast. Despite the wealth of information available on the roles of FAD2 and FAD3 in PUFA synthesis, information regarding the contributions of various Cb5 isoforms in desaturase-mediated reactions is limited. RESULTS: The present functional characterization of Cb5 polypeptides revealed that all Arabidopsis Cb5 isoforms are not similarly efficient in ω-6 desaturation, as evidenced by significant variation in their product outcomes in yeast-based functional assays. On the other hand, characterization of Cb5 polypeptides of soybean (Glycine max) suggested that similar ω-6 desaturation efficiencies were shared by various isoforms. With regard to ω-3 desaturation, certain Cb5 genes of both Arabidopsis and soybean were shown to facilitate the accumulation of more desaturation products than others when co-expressed with their native FAD3. Additionally, similar trends of differential desaturation product accumulation were also observed with most Cb5 genes of both soybean and Arabidopsis even if co-expressed with non-native FAD3. CONCLUSIONS: The present study reports the first description of the differential nature of the Cb5 genes of higher plants in fatty acid desaturation and further suggests that ω-3/ω-6 desaturation product outcome is determined by the nature of both the Cb5 isoform and the fatty acid desaturases

A Novel Replication-Competent Vaccinia Vector MVTT Is Superior to MVA for Inducing High Levels of Neutralizing Antibody via Mucosal Vaccination

Mucosal vaccination offers great advantage for inducing protective immune response to prevent viral transmission and dissemination. Here, we report our findings of a head-to-head comparison of two viral vectors modified vaccinia Ankara (MVA) and a novel replication-competent modified vaccinia Tian Tan (MVTT) for inducing neutralizing antibodies (Nabs) via intramuscular and mucosal vaccinations in mice. MVTT is an attenuated variant of the wild-type VTT, which was historically used as a smallpox vaccine for millions of Chinese people. The spike glycoprotein (S) of SARS-CoV was used as the test antigen after the S gene was constructed in the identical genomic location of two vectors to generate vaccine candidates MVTT-S and MVA-S. Using identical doses, MVTT-S induced lower levels (∼2-3-fold) of anti- SARS-CoV neutralizing antibodies (Nabs) than MVA-S through intramuscular inoculation. MVTT-S, however, was capable of inducing consistently 20-to-100-fold higher levels of Nabs than MVA-S when inoculated via either intranasal or intraoral routes. These levels of MVTT-S-induced Nab responses were substantially (∼10-fold) higher than that induced via the intramuscular route in the same experiments. Moreover, pre-exposure to the wild-type VTT via intranasal or intraoral route impaired the Nab response via the same routes of MVTT-S vaccination probably due to the pre-existing anti-VTT Nab response. The efficacy of intranasal or intraoral vaccination, however, was still 20-to-50-fold better than intramuscular inoculation despite the subcutaneous pre-exposure to wild-type VTT. Our data have implications for people who maintain low levels of anti-VTT Nabs after historical smallpox vaccination. MVTT is therefore an attractive live viral vector for mucosal vaccination

The Arabidopsis Resistance-Like Gene SNC1 Is Activated by Mutations in SRFR1 and Contributes to Resistance to the Bacterial Effector AvrRps4

The SUPPRESSOR OF rps4-RLD1 (SRFR1) gene was identified based on enhanced AvrRps4-triggered resistance in the naturally susceptible Arabidopsis accession RLD. No other phenotypic effects were recorded, and the extent of SRFR1 involvement in regulating effector-triggered immunity was unknown. Here we show that mutations in SRFR1 in the accession Columbia-0 (Col-0) lead to severe stunting and constitutive expression of the defense gene PR1. These phenotypes were temperature-dependent. A cross between srfr1-1 (RLD background) and srfr1-4 (Col-0) showed that stunting was caused by a recessive locus in Col-0. Mapping and targeted crosses identified the Col-0-specific resistance gene SNC1 as the locus that causes stunting. SRFR1 was proposed to function as a transcriptional repressor, and SNC1 is indeed overexpressed in srfr1-4. Interestingly, co-regulated genes in the SNC1 cluster are also upregulated in the srfr1-4 snc1-11 double mutant, indicating that the overexpression of SNC1 is not a secondary effect of constitutive defense activation. In addition, a Col-0 RPS4 mutant showed full susceptibility to bacteria expressing avrRps4 at 24°C but not at 22°C, while RLD susceptibility was not temperature-dependent. The rps4-2 snc1-11 double mutant showed increased, but not full, susceptibility at 22°C, indicating that additional cross-talk between resistance pathways may exist. Intriguingly, when transiently expressed in Nicotiana benthamiana, SRFR1, RPS4 and SNC1 are in a common protein complex in a cytoplasmic microsomal compartment. Our results highlight SRFR1 as a convergence point in at least a subset of TIR-NBS-LRR protein-mediated immunity in Arabidopsis. Based on the cross-talk evident from our results, they also suggest that reports of constitutive resistance phenotypes in Col-0 need to consider the possible involvement of SNC1

Use of green solvents as pre-treatment of dissolving pulp to decrease CS2 consumption from viscose production

Choline chloride-based deep eutectic solvents are widely used in biomass processing. In this work, four different green solvent mixtures were used as pre-treatment of acid sulphite dissolving pulp with the hypothesis of increasing the possibilities to produce viscose fibres and decreasing the use of the harmful and toxic carbon disulphide in the process. The experiments were performed at two different pulp to solvent mass ratios. Pulp quality parameters were also measured to determine the suitability of the pretreatment: a-cellulose, viscosity, lignin and pentosan content. In addition, X-ray diffraction analysis of pulps at the best solid to liquid ratio was performed to obtain the influence of the crystallinity index. Best results were obtained with the use of lactic acid, with reactivity values close to 94%, giving a reduction of CS2 usage of 15.83%. Furthermore, a linear relationship between the crystallinity index calculated by the XRD and reactivity with a regression factor of 0.87 was found

Regulation of microRNA biogenesis and turnover by animals and their viruses

Item does not contain fulltextMicroRNAs (miRNAs) are a ubiquitous component of gene regulatory networks that modulate the precise amounts of proteins expressed in a cell. Despite their small size, miRNA genes contain various recognition elements that enable specificity in when, where and to what extent they are expressed. The importance of precise control of miRNA expression is underscored by functional studies in model organisms and by the association between miRNA mis-expression and disease. In the last decade, identification of the pathways by which miRNAs are produced, matured and turned-over has revealed many aspects of their biogenesis that are subject to regulation. Studies in viral systems have revealed a range of mechanisms by which viruses target these pathways through viral proteins or non-coding RNAs in order to regulate cellular gene expression. In parallel, a field of study has evolved around the activation and suppression of antiviral RNA interference (RNAi) by viruses. Virus encoded suppressors of RNAi can impact miRNA biogenesis in cases where miRNA and small interfering RNA pathways converge. Here we review the literature on the mechanisms by which miRNA biogenesis and turnover are regulated in animals and the diverse strategies that viruses use to subvert or inhibit these processes