Leukemia inhibitory factor (LIF) and interleukin-6 (IL-6) are multifunctional cytokines with many similar activities. LIF is structurally and functionally related to another cytokine, Oncostatin M (OSM), that binds to the high-affinity LIF receptor but not to the low-affinity LIF receptor. A complementary DNA was isolated that encodes the high-affinity converting subunit of the LIF receptor. The converter conferred high-affinity binding of both LIF and OSM when expressed with the low-affinity LIF receptor and is identical to the signal transducing subunit of the IL-6 receptor, gp130. The gp130 subunit alone confers low-affinity binding of OSM when expressed in COS-7 cells. This receptor system resembles the high-affinity receptors for granulocyte-macrophage colony-stimulating factor, IL-3, and IL-5, which share a common subunit.
Two cDNA clones encoding a receptor for human granulocyte‐macrophage colony‐stimulating factor (hGM‐CSF‐R) were isolated by expression screening of a library made from human placental mRNA. Pools of recombinant plasmid DNA were electroporated into COS cells which were then screened for their capacity to bind radioiodinated hGM‐CSF using a sensitive microscopic autoradiographic approach. The cloned GM‐CSF‐R precursor is a 400 amino acid polypeptide (Mr 45,000) with a single transmembrane domain, a glycosylated extracellular domain and a short (54 amino acids) intracytoplasmic tail. It does not contain a tyrosine kinase domain nor show homology with members of the immunoglobulin super gene family, but does show some significant sequence homologies with receptors for several other haemopoietic growth factors, including those for interleukin‐6, erythropoietin and interleukin‐2 (beta‐chain) and also to the prolactin receptor. When transfected into COS cells the cloned cDNA directed the expression of a GM‐CSF‐R showing a single class of affinity (KD = 2(‐8) nM) and specificity for human GM‐CSF but not interleukin‐3. Messenger RNA coding for this receptor was detected in a variety of haemopoietic cells known to display hGM‐CSF binding, and cross‐linking experiments revealed a similar size for the glycosylated receptors in transfected COS and haemopoietic cells.
Leukemia inhibitory factor (LIF) is a cytokine with a broad range of activities that in many cases parallel those of interleukin‐6 (IL‐6) although LIF and IL‐6 appear to be structurally unrelated. A cDNA clone encoding the human LIF receptor was isolated by expression screening of a human placental cDNA library. The LIF receptor is related to the gp130 ‘signal‐transducing’ component of the IL‐6 receptor and to the G‐CSF receptor, with the transmembrane and cytoplasmic regions of the LIF receptor and gp130 being most closely related. This relationship suggests a common signal transduction pathway for the two receptors and may help to explain similar biological effects of the two ligands. Murine cDNAs encoding soluble LIF receptors were isolated by cross‐hybridization and share 70% amino acid sequence identity to the human sequence.
Wheat provides 20% of calories and protein consumed by humans. Recent genetic gains are <1% per annum (p.a.), insufficient to meet future demand. The Wheat Yield Consortium brings expertise in photosynthesis, crop adaptation and genetics to a common breeding platform. Theory suggest radiation use efficiency (RUE) of wheat could be increased~50%; strategies include modifying specificity, catalytic rate and regulation of Rubisco, up-regulating Calvin cycle enzymes, introducing chloroplast CO2 concentrating mechanisms, optimizing light and N distribution of canopies while minimizing photoinhibition, and increasing spike photosynthesis. Maximum yield expression will also require dynamic optimization of source: sink so that dry matter partitioning to reproductive structures is not at the cost of the roots, stems and leaves needed to maintain physiological and structural integrity. Crop development should favour spike fertility to maximize harvest index so phenology must be tailored to different photoperiods, and sensitivity to unpredictable weather must be modulated to reduce conservative responses that reduce harvest index. Strategic crossing of complementary physiological traits will be augmented with wide crossing, while genome-wide selection and high throughput phenotyping and genotyping will increase efficiency of progeny screening. To ensure investment in breeding achieves agronomic impact, sustainable crop management must also be promoted through crop improvement networks.
SummaryIn wheat, a lack of genetic diversity between breeding lines has been recognized as a significant block to future yield increases. Species belonging to bread wheat's secondary and tertiary gene pools harbour a much greater level of genetic variability, and are an important source of genes to broaden its genetic base. Introgression of novel genes from progenitors and related species has been widely employed to improve the agronomic characteristics of hexaploid wheat, but this approach has been hampered by a lack of markers that can be used to track introduced chromosome segments. Here, we describe the identification of a large number of single nucleotide polymorphisms that can be used to genotype hexaploid wheat and to identify and track introgressions from a variety of sources. We have validated these markers using an ultra‐high‐density Axiom® genotyping array to characterize a range of diploid, tetraploid and hexaploid wheat accessions and wheat relatives. To facilitate the use of these, both the markers and the associated sequence and genotype information have been made available through an interactive web site.
Leukaemia inhibitory factor (LIF) can induce macrophage differentiation in M1 murine myeloid leukaemic cells and suppress their proliferation in vitro. It does not stimulate the proliferation of normal progenitor cells and is apparently distinct from known colony‐stimulating factors. We have used oligo‐nucleotides complementary to partial amino acid sequence of LIF to isolate a LIF clone from a T lymphocyte cDNA library. When this cDNA was coupled to a yeast expression vector (YEpsec1) and introduced into yeast cells, a molecule with the biological properties characteristic of native LIF was secreted into the growth medium. The amino acid sequence of LIF established it to be a unique molecular entity, distinct from the other known haemopoietic growth factors. Since LIF is encoded by a unique gene, two biochemically separable forms of LIF probably represent post‐transcriptional or posttranslational variants of the same gene product. In contrast to several other haemopoietic regulators, the 0.8‐ to 1‐kb LIF mRNA was expressed constitutively in two murine T lymphocyte cell lines examined, and its abundance was not enhanced by stimulation with concanavalin A. Cloning, sequencing and expressing LIF has resolved several discrepancies in the literature concerning the identity of factors capable of inducing differentiation of murine myeloid leukaemic cells in vitro.
HighlightA phenotyping pipeline was used to quantify seedling root architectural traits in a wheat double haploid mapping population. QTL analyses revealed a potential major effect gene regulating seedling root vigour/growth.
SummaryDespite some notable successes, only a fraction of the genetic variation available in wild relatives has been utilized to produce superior wheat varieties. This is as a direct result of the lack of availability of suitable high‐throughput technologies to detect wheat/wild relative introgressions when they occur. Here, we report on the use of a new SNP array to detect wheat/wild relative introgressions in backcross progenies derived from interspecific hexaploid wheat/Ambylopyrum muticum F1 hybrids. The array enabled the detection and characterization of 218 genomewide wheat/Am. muticum introgressions, that is a significant step change in the generation and detection of introgressions compared to previous work in the field. Furthermore, the frequency of introgressions detected was sufficiently high to enable the construction of seven linkage groups of the Am. muticum genome, thus enabling the syntenic relationship between the wild relative and hexaploid wheat to be determined. The importance of the genetic variation from Am. muticum introduced into wheat for the development of superior varieties is discussed.
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