Dietary wheat and reduced methane yield are linked to rumen microbiome changes in dairy cows

Fermentation of pasture grasses and grains in the rumen of dairy cows and other ruminants produces methane as a by-product, wasting energy and contributing to the atmospheric load of greenhouse gasses. Many feeding trials in farmed ruminants have tested the impact of dietary components on feed efficiency, productivity and methane yield (MeY). Such diets remodel the rumen microbiome, altering bacterial, archaeal, fungal and protozoan populations, with an altered fermentation outcome. In dairy cows, some dietary grains can reduce enteric methane production. This is especially true of wheat, in comparison to corn or barley. Using a feeding trial of cows fed rolled wheat, corn or barley grain, in combination with hay and canola, we identified wheat-associated changes in the ruminal microbiome. Ruminal methane production, pH and VFA concentration data together with 16S rRNA gene amplicon sequences were used to compare ruminal bacterial and archaeal populations across diets. Differential abundance analysis of clustered sequences (OTU) identified members of the bacterial families Lachnospiraceae, Acidaminococcaceae, Eubacteriaceae, Prevotellaceae, Selenomonadaceae, Anaerovoracaceae and Fibrobacteraceae having a strong preference for growth in wheat-fed cows. Within the methanogenic archaea, (at >99% 16S rRNA sequence identity) the growth of Methanobrevibacter millerae was favoured by the non-wheat diets, while Methanobrevibacter olleyae was unaffected. From the wheat-preferring bacteria, correlation analysis found OTU strongly linked to reduced MeY, reduced pH and raised propionic acid levels. OTU from the genera Shuttleworthia and Prevotella_7 and especially Selenomonadaceae had high anti-methane correlations. An OTU likely representing (100% sequence identity) the fumarate-reducing, hydrogen-utilising, rumen bacterium Mitsuokella jalaludinii, had an especially high negative correlation coefficient (-0.83) versus MeY and moderate correlation (-0.6) with rumen pH, strongly suggesting much of the MeY suppression is due to reduced hydrogen availablity. Other OTU, representing as yet unknown species from the Selenomonadaceae family and the genera Prevotella_7, Fibrobacter and Syntrophococcus also had high to moderate negative MeY correlations, but low correlation with pH. These latter likely represent bacterial species able to reduce MeY without causing greater ruminal acidity, making them excellent candidates, provided they can be isolated, for development as anti-methane probiotics.

Genome-wide association studies dissect the G × E interaction for agronomic traits in a worldwide collection of safflowers (Carthamus tinctorius L.)

Genome-wide association studies were conducted using a globally diverse safflower (Carthamus tinctorius L.) Genebank collection for grain yield (YP), days to flowering (DF), plant height (PH), 500 seed weight (SW), seed oil content (OL), and crude protein content (PR) in four environments (sites) that differed in water availability. Phenotypic variation was observed for all traits. YP exhibited low overall genetic correlations (rGoverall) across sites, while SW and OL had high rGoverall and high pairwise genetic correlations (rGij) across all pairwise sites. In total, 92 marker-trait associations (MTAs) were identified using three methods, single locus genome-wide association studies (GWAS) using a mixed linear model (MLM), the Bayesian multi-locus method (BayesR), and meta-GWAS. MTAs with large effects across all sites were detected for OL, SW, and PR, and MTAs specific for the different water stress sites were identified for all traits. Five MTAs were associated with multiple traits; 4 of 5 MTAs were variously associated with the three traits of SW, OL, and PR. This study provided insights into the phenotypic variability and genetic architecture of important safflower agronomic traits under different environments.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-022-01295-8.

Faecalibacterium diversity in dairy cow milk

The bacterial species, Faecalibacterium prausnitzii, beneficial to humans and animals and found in mammalian and avian gut, is also occasionally found in dairy cow milk. It is one of the butyrate-producing bacteria of the colon, has anti-inflammatory properties and its abundance in the gut is negatively correlated with obesity in humans. Several strains differing in their functional capability, have been identified. It is important therefore, milk being a potential source of F. prausnitzii as a novel probiotic, to investigate the diversity of this species in bovine milk. Using 16s rRNA gene amplicons we find 292 different dereplicated Faecalibacterium-related amplicons in a herd of 21 dairy cows. The distribution of the 20 most abundant amplicons with >97% identity to a Greengenes OTU varies from cow to cow. Clustering of the 292 pooled sequences from all cows at 99.6% identity finds 4 likely Faecalibacterium phylotypes with >98.5% identity to an F. prausnitzii reference sequence. Sequence alignment and phylogenetic analysis shows these phylotypes are distinct from 34 other species from the Ruminococcaceae family and displaying the sequence clusters as a network illustrates how each cluster is composed of sequences from multiple cows. We conclude there are several phylotypes of Faecalibacterium prausnitzii (the only species so far defined for the genus) in this dairy herd with cows being inoculated with a mixture of several strains from a common source. We conclude that not only can Faecalibacterium be detected in dairy cow milk (as noted by others) but that there exist multiple different strains in the milk of a dairy herd. Therefore milk, as an alternative to faeces, offers the opportunity of discovering new strains with potential probiotic application.

Metabolomics approaches for the discrimination of disease suppressive soils for Rhizoctonia solani AG8 in cereal crops using 1H NMR and LC-MS

The suppression of soilborne crop pathogens such as Rhizoctonia solani AG8 may offer a sustainable and enduring method for disease control, though soils with these properties are difficult to identify. In this study, we analysed the soil metabolic profiles of suppressive and non-suppressive soils over 2 years of cereal production. We collected bulk and rhizosphere soil at different cropping stages and subjected soil extracts to liquid chromatography-mass spectrometry (LC-MS) and proton nuclear magnetic resonance spectroscopy (¹H NMR) analyses. Community analyses of suppressive and non-suppressive soils using principal component analyses and predictive modelling of LC-MS and NMR datasets respectively, revealed distinct biochemical profiles for the two soil types with clustering based on suppressiveness and cropping stage. NMR spectra revealed the suppressive soils to be more abundant in sugar molecules than non-suppressive soils, which were more abundant in lipids and terpenes. LC-MS features that were significantly more abundant in the suppressive soil were identified and assessed as potential biomarkers for disease suppression. The structures of a potential class of LC-MS biomarkers were elucidated using accurate mass data and MS fragmentation spectrum information. The most abundant compound found in association with suppressive soils was confirmed to be a macrocarpal, which is an antimicrobial secondary metabolite. Our study has demonstrated the utility of environmental metabolomics for the study of disease suppressive soils, resulting in the discovery of a macrocarpal biomarker for R. solani AG8 suppressive soil which can be further studied functionally in association with suppression pot trials and microbial isolation studies.

Comparative Metatranscriptomics of Wheat Rhizosphere Microbiomes in Disease Suppressive and Non-suppressive Soils for Rhizoctonia solani AG8

The soilborne fungus Rhizoctonia solani anastomosis group (AG) 8 is a major pathogen of grain crops resulting in substantial production losses. In the absence of resistant cultivars of wheat or barley, a sustainable and enduring method for disease control may lie in the enhancement of biological disease suppression. Evidence of effective biological control of R. solani AG8 through disease suppression has been well documented at our study site in Avon, South Australia. A comparative metatranscriptomic approach was applied to assess the taxonomic and functional characteristics of the rhizosphere microbiome of wheat plants grown in adjacent fields which are suppressive and non-suppressive to the plant pathogen R. solani AG8. Analysis of 12 rhizosphere metatranscriptomes (six per field) was undertaken using two bioinformatic approaches involving unassembled and assembled reads. Differential expression analysis showed the dominant taxa in the rhizosphere based on mRNA annotation were Arthrobacter spp. and Pseudomonas spp. for non-suppressive samples and Stenotrophomonas spp. and Buttiauxella spp. for the suppressive samples. The assembled metatranscriptome analysis identified more differentially expressed genes than the unassembled analysis in the comparison of suppressive and non-suppressive samples. Suppressive samples showed greater expression of a polyketide cyclase, a terpenoid biosynthesis backbone gene (dxs) and many cold shock proteins (csp). Non-suppressive samples were characterised by greater expression of antibiotic genes such as non-heme chloroperoxidase (cpo) which is involved in pyrrolnitrin synthesis, and phenazine biosynthesis family protein F (phzF) and its transcriptional activator protein (phzR). A large number of genes involved in detoxifying reactive oxygen species (ROS) and superoxide radicals (sod, cat, ahp, bcp, gpx1, trx) were also expressed in the non-suppressive rhizosphere samples most likely in response to the infection of wheat roots by R. solani AG8. Together these results provide new insight into microbial gene expression in the rhizosphere of wheat in soils suppressive and non-suppressive to R. solani AG8. The approach taken and the genes involved in these functions provide direction for future studies to determine more precisely the molecular interplay of plant-microbe-pathogen interactions with the ultimate goal of the development of management options that promote beneficial rhizosphere microflora to reduce R. solani AG8 infection of crops.

Transcriptome sequencing of field pea and faba bean for discovery and validation of SSR genetic markers

BACKGROUND

Field pea (Pisum sativum L.) and faba bean (Vicia faba L.) are cool-season grain legume species that provide rich sources of food for humans and fodder for livestock. To date, both species have been relative 'genomic orphans' due to limited availability of genetic and genomic information. A significant enrichment of genomic resources is consequently required in order to understand the genetic architecture of important agronomic traits, and to support germplasm enhancement, genetic diversity, population structure and demographic studies.

RESULTS

cDNA samples obtained from various tissue types of specific field pea and faba bean genotypes were sequenced using 454 Roche GS FLX Titanium technology. A total of 720,324 and 304,680 reads for field pea and faba bean, respectively, were de novo assembled to generate sets of 70,682 and 60,440 unigenes. Consensus sequences were compared against the genome of the model legume species Medicago truncatula Gaertn., as well as that of the more distantly related, but better-characterised genome of Arabidopsis thaliana L.. In comparison to M. truncatula coding sequences, 11,737 and 10,179 unique hits were obtained from field pea and faba bean. Totals of 22,057 field pea and 18,052 faba bean unigenes were subsequently annotated from GenBank. Comparison to the genome of soybean (Glycine max L.) resulted in 19,451 unique hits for field pea and 16,497 unique hits for faba bean, corresponding to c. 35% and 30% of the known gene space, respectively. Simple sequence repeat (SSR)-containing expressed sequence tags (ESTs) were identified from consensus sequences, and totals of 2,397 and 802 primer pairs were designed for field pea and faba bean. Subsets of 96 EST-SSR markers were screened for validation across modest panels of field pea and faba bean cultivars, as well as related non-domesticated species. For field pea, 86 primer pairs successfully obtained amplification products from one or more template genotypes, of which 59% revealed polymorphism between 6 genotypes. In the case of faba bean, 81 primer pairs displayed successful amplification, of which 48% detected polymorphism.

CONCLUSIONS

The generation of EST datasets for field pea and faba bean has permitted effective unigene identification and functional sequence annotation. EST-SSR loci were detected at incidences of 14-17%, permitting design of comprehensive sets of primer pairs. The subsets from these primer pairs proved highly useful for polymorphism detection within Pisum and Vicia germplasm.

Transcriptome sequencing of lentil based on second-generation technology permits large-scale unigene assembly and SSR marker discovery

Background

Lentil (Lens culinaris Medik.) is a cool-season grain legume which provides a rich source of protein for human consumption. In terms of genomic resources, lentil is relatively underdeveloped, in comparison to other Fabaceae species, with limited available data. There is hence a significant need to enhance such resources in order to identify novel genes and alleles for molecular breeding to increase crop productivity and quality.

Results

Tissue-specific cDNA samples from six distinct lentil genotypes were sequenced using Roche 454 GS-FLX Titanium technology, generating c. 1.38 × 10⁶ expressed sequence tags (ESTs). De novo assembly generated a total of 15,354 contigs and 68,715 singletons. The complete unigene set was sequence-analysed against genome drafts of the model legume species Medicago truncatula and Arabidopsis thaliana to identify 12,639, and 7,476 unique matches, respectively. When compared to the genome of Glycine max, a total of 20,419 unique hits were observed corresponding to c. 31% of the known gene space. A total of 25,592 lentil unigenes were subsequently annoated from GenBank. Simple sequence repeat (SSR)-containing ESTs were identified from consensus sequences and a total of 2,393 primer pairs were designed. A subset of 192 EST-SSR markers was screened for validation across a panel 12 cultivated lentil genotypes and one wild relative species. A total of 166 primer pairs obtained successful amplification, of which 47.5% detected genetic polymorphism.

Conclusions

A substantial collection of ESTs has been developed from sequence analysis of lentil genotypes using second-generation technology, permitting unigene definition across a broad range of functional categories. As well as providing resources for functional genomics studies, the unigene set has permitted significant enhancement of the number of publicly-available molecular genetic markers as tools for improvement of this species.

A neurotropic herpesvirus infecting the gastropod, abalone, shares ancestry with oyster herpesvirus and a herpesvirus associated with the amphioxus genome

Background

With the exception of the oyster herpesvirus OsHV-1, all herpesviruses characterized thus far infect only vertebrates. Some cause neurological disease in their hosts, while others replicate or become latent in neurological tissues. Recently a new herpesvirus causing ganglioneuritis in abalone, a gastropod, was discovered. Molecular analysis of new herpesviruses, such as this one and others, still to be discovered in invertebrates, will provide insight into the evolution of herpesviruses.

Results

We sequenced the genome of a neurotropic virus linked to a fatal ganglioneuritis devastating parts of a valuable wild abalone fishery in Australia. We show that the newly identified virus forms part of an ancient clade with its nearest relatives being a herpesvirus infecting bivalves (oyster) and, unexpectedly, one we identified, from published data, apparently integrated within the genome of amphioxus, an invertebrate chordate. Predicted protein sequences from the abalone virus genome have significant similarity to several herpesvirus proteins including the DNA packaging ATPase subunit of (putative) terminase and DNA polymerase. Conservation of amino acid sequences in the terminase across all herpesviruses and phylogenetic analysis using the DNA polymerase and terminase proteins demonstrate that the herpesviruses infecting the molluscs, oyster and abalone, are distantly related. The terminase and polymerase protein sequences from the putative amphioxus herpesvirus share more sequence similarity with those of the mollusc viruses than with sequences from any of the vertebrate herpesviruses analysed.

Conclusions

A family of mollusc herpesviruses, Malacoherpesviridae, that was based on a single virus infecting oyster can now be further established by including a distantly related herpesvirus infecting abalone, which, like many vertebrate viruses is neurotropic. The genome of Branchiostoma floridae (amphioxus) provides evidence for the existence of a herpesvirus associated with this invertebrate chordate. The virus which likely infected amphioxus is, by molecular phylogenetic analysis, more closely related to the other 2 invertebrate viruses than to herpesviruses infecting vertebrates (ie chordates).

Power of a genome scan to detect and locate quantitative trait loci in cattle using dense single nucleotide polymorphisms

There is increasing use of dense single nucleotide polymorphisms (SNPs) for whole-genome association studies (WGAS) in livestock to map and identify quantitative trait loci (QTL). These studies rely on linkage disequilibrium (LD) to detect an association between SNP genotypes and phenotypes. The power and precision of these WGAS are unknown, and will depend on the extent of LD in the experimental population. One complication for WGAS in livestock populations is that they typically consist of many paternal half-sib families, and in some cases full-sib families; unless this subtle population stratification is accounted for, many spurious associations may be reported. Our aim was to investigate the power, precision and false discovery rates of WGAS for QTL discovery, with a commercial SNP array, given existing patterns of LD in cattle. We also tested the efficiency of selective genotyping animals. A total of 365 cattle were genotyped for 9232 SNPs. We simulated a QTL effect as well as polygenic and environmental effects for all animals. One QTL was simulated on a randomly chosen SNP and accounted for 5%, 10% or 18% of the total variance. The power to detect a moderate-sized additive QTL (5% of the phenotypic variance) with 365 animals genotyped was 37% (p < 0.001). Most importantly, if pedigree structure was not accounted for, the number of false positives significantly increased above those expected by chance alone. Selective genotyping also resulted in a significant increase in false positives, even when pedigree structure was accounted for.

Haemonchus contortus: molecular characterisation of a small heat shock protein

A cDNA encoding a predicted small heat shock protein, HSP20, was isolated from the parasitic nematode Haemonchus contortus. This cDNA encoded a predicted protein of 156 amino acids, which had high sequence identity with other nematode small heat shock proteins. Southern blot analysis of genomic DNA suggested that in H. contortus HSP20 is encoded by a single copy gene. The HSP20 transcript and protein were expressed in the infective larvae (L3), early L4 and adult stages, but expression was not increased by heat shock treatment. In situ hybridisation analysis was used to localise expression of HSP20 mRNA in the adult parasite. Similar HSPs (heat shock protein) were detected by Western blotting in Ancylostoma caninum, Dictyocaulus viviparus, and Toxocara canis, but not in Trichostronglyus colubriformis. The conservation of HSP20 in several different nematode species may reflect its importance to parasites that require mammalian hosts as a part of their development. Index Descriptors and Abbreviations: Haemonchus contortus; nematode; small heat shock protein; L3, infective larvae; xL3, exsheathed L3; eL4, early L4; EST, expressed sequence tag; HSP20, heat shock protein 20; sHSP, small heat shock protein

Analysis of developmentally regulated genes of the parasite Haemonchus contortus

Differential regulation of gene expression in the development of Haemonchus contortus was analysed using RNA arbitrarily-primed PCR. A study of third-stage larval and adult H. contortus revealed large differences between the two stages; 32 and 30% unique third-stage larval and adult RNA arbitrarily-primed PCR products, respectively. This finding is consistent with a high degree of differential gene expression between these developmental stages. A number of adult products were sequenced, revealing 11 molecules to be similar to deposits within sequence databases. Four other molecules that did not have significant similarity to sequences in the databases may represent developmentally regulated genes specific to H. contortus. Northern analysis of the putative adult-expressed molecules with homologues in the databases confirmed that four were expressed only in adults, while four were expressed in both stages, but had different sized transcripts. This may reflect differential splicing, or expression of closely related but different molecules at different life cycle stages. Two molecules were present in mRNA populations from both stages, suggesting these were false stage-associated molecules. No transcript was detected for one molecule by Northern analysis, probably due to low level of expression. In situ hybridisation analysis was used to localise expression of transcripts in the adult parasite, in particular, to gain some insight into the nature of those molecules with no known predicted function.

Isolation and characterisation of the carnation floral-specific MADS box gene, CMB2

The cDNA clone KD81, was isolated from a carnation petal cDNA library based on its strong differential expression in petals compared with leaves. The deduced amino acid sequence of KD81 indicated high homology with members of the MADS box family of transcription factors. Identified within the deduced amino acid sequence are two conserved domains; an N-terminal, MADS box and a central, K box. The gene encoding KD81 was termed Carnation MADS Box gene 2 (CMB2). Expression of CMB2 is floral-specific and in petal, transcripts were persistent from the initial stages of development through flower opening. Transcripts were not detected in vegetative tissues. The CMB2 protein is most homologous to TDR6 from tomato, the product of the petal and stamen identity gene DEFICIENS (DEFA), and several DEFA homologues including SLM3, STDEF, PMADS1 and APETALA3. Southern blot analysis indicated that CMB2 is present as a single copy within the carnation genome. Characterisation of a genomic clone encoding CMB2, revealed the molecular structure of CMB2 to be consistent with that reported for other plant MADS box genes. Analysis of the CMB2 promoter sequence revealed the presence of two putative cis-acting elements known as serum response elements (SREs). These elements are proposed as the target for MADS box domain binding and may be involved in the regulation/autoregulation of gene expression. CMB2 represents the first reported isolation of a MADS box gene from carnation.

Characterization of the mRNA encoding a proline-rich 37-kilodalton glycoprotein from the excretory-secretory products of Trichostrongylus colubriformis

A glycoprotein, with apparent molecular weight in SDS-polyacrylamide gels of 37 kDa, has been isolated from the excretory-secretory (ES) products of the adult stage of Trichostrongylus colubriformis, a parasitic nematode. This protein is the major ES product recognized in immunoblots by lymph from a naturally infected sheep. A synthetic oligonucleotide, based on peptide sequence data from a digest of the purified protein was used to successfully screen a cDNA library. A cDNA clone was isolated which encoded a presumptive protein precursor of 220 amino acids that contained a 63 amino acid region of which more than 35% of the residues were proline, three peptide sequences determined from the natural component, and three potential N-glycosylation sites, consistent with the protein being isolated from the lectin-bound fraction of the adult ES products. The presumptive, processed, amino terminus encoded by the cDNA clone was preceded by a signal-like, hydrophobic-rich region of 16 amino acids.

Improved shuttle vectors for cloning and high-level Cu(2+)-mediated expression of foreign genes in yeast

New yeast episomal vectors having a high degree of utility for cloning and expression in Saccharomyces cerevisiae are described. One vector, pYEULlacZ, is based on pUC19 and employs the pUC19 multiple cloning site for the selection of recombinants in Escherichia coli by lacZ inactivation. In addition, the vector contains two genes, URA3 and leu2-d, for selection of the plasmid in ura3 or leu2 yeast strains. The presence of the leu2-d gene appears to promote replication at high copy numbers. The introduction of CUP1 cassettes allows these plasmids to direct Cu(2+)-regulated production of foreign proteins in yeast. We show the production of a helminth antigen as an example of the vector application.

Characterization, cloning and host-protective activity of a 30-kilodalton glycoprotein secreted by the parasitic stages of Trichostrongylus colubriformis

The helminth Trichostrongylus colubriformis is a parasitic nematode infecting the small intestine of sheep. We report the isolation and characterization of a 30-kDa glycoprotein capable of partially protecting guinea-pigs against the parasite. This glycoprotein is secreted by the L4 and adult parasitic stages of the worm. The sequence of three separate cDNA clones predicts the polypeptide to be about 15 kDa, with four N-linked carbohydrate chains and an internal disulphide bond. The clones also indicate the existence of sequence variability in this antigen. Limited sequence homology to a porcine intestinal peptide suggests an influence on host gut physiology.

Characterization of cDNA clones coding for muscle tropomyosin of the nematode Trichostrongylus colubriformis

The host-protective antigen from detergent-solubilised extracts of the sheep intestinal helminth Trichostrongylus colubriformis has been identified as tropomyosin. Complementary DNA clones coding for T. colubriformis muscle tropomyosin have been isolated and characterised as the first step in obtaining recombinant protein to carry out more extensive vaccination trials. The clones represent an mRNA of 1544 bases, including a relatively long 5' untranslated sequence of 307 bases and a 3' non-coding region of 344 bases. The mRNA codes for a highly alpha-helical protein of 284 residues with a molecular weight of 33,000; characteristics typically observed for the muscle tropomyosins of higher organisms. The T. colubriformis protein has 58% sequence identity with rabbit and Drosophila melanogaster muscle tropomyosins, and the differences in the protein sequence are randomly distributed throughout the molecule. There is complete identity between the three sequences for the N-terminal 9 residues, the region believed to be essential for the polymerisation of tropomyosin molecules and for binding to actin and troponin.

Two families of abl-related transcripts in human haematopoietic cells differing in their homology to v-abl

The transforming gene of the Abelson murine leukaemia virus, v-abl, contains two open reading frames (orf). The 5' orf encodes a tyrosine-specific protein kinase while the 3' orf has the capacity to code for an 18,000 Mr protein. However, no 3' orf product has yet been identified. Using probes capable of distinguishing between the 5' and 3' orfs of v-abl, we have examined the abl-related transcripts present in human haematopoietic cells and leukaemia-derived cell lines, including the chronic myeloid leukaemia-derived cell line K562. Our results indicate that transcripts of 6 kb, 7 kb and 8 kb (kilobase, 10(3) base-pairs) show strong homology to v-abl 5' protein kinase-encoding orf sequences, but are devoid of any sequences from the v-abl 3' orf. In addition, transcripts of 5 kb, 3 kb, 1.6 kb and 1.4 kb, reacting with both 5' orf and 3' orf probes, were observed. The latter species, with coding sequences from both the tyrosine kinase and the putative 18,000 Mr protein, must be transcribed from the human c-abl gene as this is apparently the only human gene containing sequences homologous to the v-abl 3' orf. The 6 kb, 7 kb and 8 kb transcripts may arise either from the c-abl gene through differential splicing, or from one of the three other regions of the human genome with sequences homologous to the 5' orf of v-abl. Examination of genomic DNA from the K562 cell line revealed that the amplification of abl-related sequences, which is presumed to result in the elevated levels of the 8 kb transcript found in this cell line, does not involve sequences homologous to the v-abl 3' orf. This lends credence to the idea that the 8 kb transcript may derive from an abl-related gene other than c-abl. While the significance of the 3' orf of v-abl remains unknown, the data presented strongly suggest the existence of at least two distinct abl-related proteins in human haematopoietic cells.

Changes in the expression of membrane antigens during the differentiation of chicken erythroblasts

Chicken erythroblasts can be transformed by the avian retrovirus, avian erythroblastosis virus (AEV). Earlier studies have shown that the mechanism of transformation appears to involve a "block" in differentiation, in that when erythroblasts are transformed by a temperature-sensitive mutant of ts34 AEV and incubated at the nonpermissive temperature, the cells start to differentiate and produce hemoglobin. We have decided to use this system to isolate pure populations of chicken erythroblasts and raise monoclonal antibodies against their cell surface proteins. Three monoclonal antibodies were isolated and tested for their ability to bind to various hematopoietic cell types; two were shown to be erythroid-specific, whereas the other antibody bound to proliferating cells but not to erythrocytes or granulocytes. Of the erythroid-specific antibodies, one precipitated a 94,000 molecular weight protein, whereas the other precipitated a 11,000 molecular weight protein that was tentatively identified as hemoglobin. The use of this system and approach to identify and evaluate changes that occur during the differentiation is discussed.

Cell-surface glycoprotein synthesis during differentiation of chicken erythroblasts transformed by temperature-sensitive avian erythroblastosis virus

Chicken erythroblasts transformed by a temperature-sensitive mutant of avian erythroblastosis virus (ts34 AEV) have a greatly increased haemoglobin content (Graf, T., N. Ade and H. Beug: Nature 275, 496-501 (1978)) if allowed to grow for 3-5 days at the non-permissive temperature (41 degrees C), instead of the permissive temperature (35 degrees C) of the virus. Cell-surface molecular changes during this differentiation were investigated by examining the glycoproteins synthesized by a ts34-transformed erythroblast cell line. These cells synthesized a greatly increased amount of a 94,000 molecular weight erythrocyte cell-surface glycoprotein beginning 2-6 h after a shift in growth temperature from 35 degrees to 41 degrees C, consistent with the proposal that such a shift releases these transformed cells from a differentiation block.