A Pyramid Breeding of Eight Grain-yield Related Quantitative Trait Loci Based on Marker-assistant and Phenotype Selection in Rice （Oryza sativa L.）

1000-Grain weight and spikelet number per panicle are two important components for rice grain yield.In our previous study,eight quantitative trait loci(QTLs)conferring spikelet number per panicle and 1000-grain weight were mapped through sequencing-based genotyping of 150 rice recombinant inbred lines(RILs).In this study,we validated the effects of four QTLs from Nipponbare using chromosome segment substitution lines(CSSLs),and pyramided eight grain yield related QTLs.The new lines containing the eight QTLs with positive effects showed increased panicle and spikelet size as compared with the parent variety 93-11.We further proposed a novel pyramid breeding scheme based on marker-assistant and phenotype selection(MAPS).This scheme allowed pyramiding of as many as 24 QTLs at a single hybridization without massive cross work.This study provided insights into the molecular basis of rice grain yield for direct wealth for high-yielding rice breeding.     

Molecular mapping and physical location of major gene conferring seedling resistance to Septoria tritici blotch in wheat

Septoria tritici blotch (STB) caused by Mycosphaerella graminicola (anamorph: Septoria tritici), is one of the most important foliar diseases of wheat. We assessed three doubled-haploid (DH) populations derived from Chara (STB-susceptible)/WW2449 (STB-resistant), Whistler (STB-susceptible)/WW1842 (STB-resistant) and Krichauff (STB susceptible)/WW2451 (STB-resistant) for resistance to a single-pycnidium isolate 79.2.1A of M. graminicola at the seedling stage. STB resistance in each of the three DH populations was conditioned by a single major gene designated as StbWW2449, StbWW1842 and StbWW2451. Linkage analyses and physical mapping indicated that the StbWW loci were located on the short arm of chromosome 1B (IBS). Four simple sequence repeat (SSR) markers linked with STB resistance: Xwmc230, Xbarc119b, Xksum045 and Xbarc008 were located to the distal bin of 1BS.sat1BS-4 (FL: 0.52–1.00) in the 1BS physical map. Xwmc230, Xbarc119b and Xksum045 markers, mapped within 7 cM from StbWW were validated for their linkage and predicted the STB resistance with over 94% accuracy in the 79 advanced breeding lines having WW2449 as one of the parents. The marker interval Xwmc230/Xksum045-Xbarc119b also explained up to 38% of the phenotypic variance at the adult plant stage in all three DH mapping populations. These results have proven that SSR markers are useful in monitoring STB resistance both at seedling and adult plant stages and hence are suitable for routine marker-assisted selection in the wheat breeding programs. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cloning of a DNA region from Bradyrhizobium japonicum encoding pleiotropic functions in heme metabolism and respiration

Random and site-directed Tn5-induced mutagenesis of Bradyrhizobium japonicum yielded two mutations, one in strain 2960 and the other in strain 2606::Tn5-20, which mapped close to each other but in separate genes. The corresponding wild-type genes were cloned, and their approximate location on the cloned DNA was determined. Mutant 2960 was Fix^- and formed green nodules on soybean, whereas strain 2606::Tn5-20 had ca. 4% of wild-type Fix activity and formed white nodules. Cytochrome oxidase assays (Nadi tests) showed a negative reaction with both mutants, indicating a functional deficiency of cytochrome c or its terminal oxidase or both. However, the mutants grew well under aerobic conditions on minimal media with different carbon sources. Furthermore, mutant 2960 had a reduced activity in hydrogen uptake, was unable to grow anaerobically with nitrate as the terminal electron acceptor and 2960-infected soybean nodules contained little, if any, functional leghemoglobin. Southern blot analysis showed that a B. japonicum heme biosynthesis mutant [strain LO505: O'Brian MR, Kirshbom PM, Maier RJ (1987) Proc Natl Acad Sci USA 84: 8390–8393] had its mutation close to the Tn5 insertion site of our mutant 2606::Tn5-20. This finding, combined with the observed phenotypes, suggested that the genes affected in mutants 2960 and 2606::Tn5-20 were involved in some steps of heme biosynthesis thus explaining the pleiotropic respiratory deficiencies of the mutants. Similar to strain LO505, the mutant 2606::Tn5-20 (but not 2960) was defective in the activity of protoporphyrinogen IX oxidase which catalyzes the penultimate step in the heme biosynthesis pathway. This suggests that one of the two cloned genes may code for this enzyme.     

Comparison of genetic and cytogenetic maps of hexaploid wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) using SSR and DArT markers

A number of technologies are available to increase the abundance of DNA markers and contribute to developing high resolution genetic maps suitable for genetic analysis. The aim of this study was to expand the number of Diversity Array Technology (DArT) markers on the wheat array that can be mapped in the wheat genome, and to determine their chromosomal location with respect to simple sequence repeat (SSR) markers and their position on the cytogenetic map. A total of 749 and 512 individual DArT and SSR markers, respectively, were identified on at least one of four genetic maps derived from recombinant inbred line (RIL) or doubled haploid (DH) populations. A number of clustered DArT markers were observed in each genetic map, in which 20–34% of markers were redundant. Segregation distortion of DArT and SSR markers was also observed in each mapping population. Only 14% of markers on the Version 2.0 wheat array were assigned to chromosomal bins by deletion mapping using aneuploid lines. In this regard, methylation effects need to be considered when applying DArT marker in genetic mapping. However, deletion mapping of DArT markers provides a reference to align genetic and cytogenetic maps and estimate the coverage of DNA markers across the wheat genome. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mapping and diagnostic marker development for Soil-borne cereal mosaic virus resistance in bread wheat

Monogenically-inherited resistance to Soil-borne cereal mosaic virus (SBCMV) in hexaploid bread wheat cultivars ‘Tremie’ and ‘Claire’ was mapped on chromosome 5D. The two closest flanking markers identified in the Claire-derived mapping population, Xgwm469-5D and E37M49, are linked to the resistance locus at distances of 1 and 9 cm, respectively. Xgwm469-5D co-segregated with the SBCMV resistance in the Tremie-derived population and with the recently identified Sbm1 locus in the cv. Cadenza. This suggested that Tremie and Claire carry a resistance gene allelic to Sbm1, or one closely linked to it. The diagnostic value of Xgwm469-5D was assessed using a collection of SBCMV resistant and susceptible cultivars. Importantly, all susceptible genotypes carried a null allele of Xgwm469-5D, whereas resistant genotypes presumably related to either Claire and Tremie or Cadenza revealed a 152 or 154 bp allele of Xgwm469-5D, respectively. Therefore, Xgwm469-5D is well suited for marker assisted selection for SBCMV resistance.     

Revealing the genetic architecture of FHB resistance in hexaploid wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) by QTL meta-analysis

Fusarium head blight (FHB) in wheat results in reduced yield and quality and in accumulation of mycotoxins. The objective of this study was to identify genomic regions in wheat involved in the control of FHB resistance applying a QTL meta-analysis approach by combining QTL of 30 mapping populations to propose independent meta-QTL (MQTL). A consensus map was created on which initial QTL were projected. Nineteen MQTL comprising 2–13 initial QTL with widely varying confidence intervals were found on 12 chromosomes. Some of them coincided with genomic regions previously identified (e.g. chromosomes 3BS, 6B), however, some MQTL were newly detected by this study. Separate analysis of populations with the same resistant parent showed a rather high consistency for the Chinese spring wheat donor ‘Sumai 3’, but little consistency for the Chinese donor ‘Wangshuibai’ and the Swiss donor ‘Arina’. According to our results breeders can in future (1) choose parents for crossing not comprising the same resistance loci or QTL intervals, (2) exploit new MQTL, and (3) select markers of some of these MQTL to be used in marker-assisted selection. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

PTPD1 supports receptor stability and mitogenic signaling in bladder cancer cells

PTPD1, a cytosolic non-receptor protein-tyrosine phosphatase, stimulates the Src-EGF transduction pathway. Localization of PTPD1 at actin cytoskeleton and adhesion sites is required for cell scattering and migration. Here, we show that during EGF stimulation, PTPD1 is rapidly recruited to endocytic vesicles containing the EGF receptor. Endosomal localization of PTPD1 is mediated by interaction with KIF16B, an endosomal kinesin that modulates receptor recycling at the plasma membrane. Silencing of PTPD1 promotes degradation of EGF receptor and inhibits downstream ERK signaling. We also found that PTPD1 is markedly increased in bladder cancer tissue samples. PTPD1 levels positively correlated with the grading and invasiveness potential of these tumors. Transgenic expression of an inactive PTPD1 mutant or genetic knockdown of the endogenous PTPD1 severely inhibited both growth and motility of human bladder cancer cells. These findings identify PTPD1 as a novel component of the endocytic machinery that impacts on EGF receptor stability and on growth and motility of bladder cancer cells.     

Mucin 21/Epiglycanin Modulates Cell Adhesion

The molecular structure of mouse Mucin 21 (Muc21)/epiglycanin is proposed to have 98 tandem repeats of 15 amino acids and three exceptional repeats with 12 or 13 amino acids each, followed by a stem domain, a transmembrane domain, and a cytoplasmic tail. A cDNA of Muc21 having 84 tandem repeats of 15 amino acids was constructed and transfected using a Venus vector into HEK 293T cells. The fluorescent cells, which were considered to express Muc21, were nonadherent. This antiadhesion effect was lessened when constructs with smaller numbers of tandem repeats were used, suggesting that the tandem repeat domain plays a crucial role. Cells expressing Muc21 were significantly less adherent to each other and to extracellular matrix components than control cells. Antibody binding to the cell surface integrin subunits α5, α6, and β1 was reduced in Muc21 transfectants in a tandem repeat-dependent manner, whereas equal amounts of proteins were detected by Western blot analysis. Muc21 was expressed as a large glycoprotein that was highly glycosylated with O-glycans at the cell surface, as detected by flow cytometry, Western blotting, and lectin blotting. Although at least a portion of Muc21 was glycosylated with sialylated glycans, removal of sialic acid did not influence the prevention of adhesion.