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K S Wu

Publications and source records attributed to K S Wu.

16 recordsLinked to original sources
PubMed2000

tA single amino acid difference distinguishes resistant and susceptible alleles of the rice blast resistance gene Pi-ta.

The rice blast resistance (R) gene Pi-ta mediates gene-for-gene resistance against strains of the fungus Magnaporthe grisea that express avirulent alleles of AVR-Pita. Using a map-based cloning strategy, we cloned Pi-ta, which is linked to the centromere of chromosome 12. Pi-ta encodes a predicted 928-amino acid cytoplasmic receptor with a centrally localized nucleotide binding site. A single-copy gene, Pi-ta shows low constitutive expression in both resistant and susceptible rice. Susceptible rice varieties contain pi-ta(-) alleles encoding predicted proteins that share a single amino acid difference relative to the Pi-ta resistance protein: serine instead of alanine at position 918. Transient expression in rice cells of a Pi-ta(+) R gene together with AVR-Pita(+) induces a resistance response. No resistance response is induced in transient assays that use a naturally occurring pi-ta(-) allele differing only by the serine at position 918. Rice varieties reported to have the linked Pi-ta(2) gene contain Pi-ta plus at least one other R gene, potentially explaining the broadened resistance spectrum of Pi-ta(2) relative to Pi-ta. Molecular cloning of the AVR-Pita and Pi-ta genes will aid in deployment of R genes for effective genetic control of rice blast disease.

Alleles↗
PubMed1993

Genetic and physical mapping of telomeres and macrosatellites of rice.

Telomeres and telomere-associated satellites of rice were genetically and physically analyzed by pulsed-field gel electrophoresis (PFGE) using Arabidopsis telomeric DNA and rice satellite sequences as probes. We demonstrate that Arabidopsis telomeric sequences hybridize to rice telomeres under the conditions of high stringency. Using the Arabidopsis probe, multiple, discrete telomeric fragments could be identified on pulsed-field gel blots of rice DNAs digested with rare-cutting restriction enzymes. Most of the telomeric bands larger than 300 kb are physically linked with satellite bands as revealed by PFGE. Some of the telomeric and satellite bands segregate in a Mendelian fashion and are highly reproducible. Three such telomeric bands have been mapped to the distal ends of RFLP linkage groups: Telsm-1 on chromosome 8, Telsa-1 on chromosome 9 and Telsm-3 on chromosome 11. One segregating satellite band was mapped to an internal region of chromosome 10. Telomeric fragments were shown not only to be genetically linked to but also physically linked (based on PFGE) to the terminal RFLP markers. The physical distance from telomeric sequences to a distal RFLP marker, r45s gene, on chromosome 9, is 200 kb while the distance from telomeric sequences to RG98, a terminal RFLP marker on chromosome 11, is 260 kb. Physical maps of the telomere regions of chromosome 9 and chromosome 11 are presented.

Arabidopsis↗
PubMed1993

PFGE analysis of the rice genome: estimation of fragment sizes, organization of repetitive sequences and relationships between genetic and physical distances.

Pulsed-field gel electrophoresis (PFGE) has been applied to analyze the rice nuclear genome. Probing 56 RFLP probes selected from the 12 rice chromosomes to PFGE blots of nine rare-cutting restriction enzymes revealed that there are relatively high numbers of 'rare-cutting' restriction sites in the rice genome. The average sizes of restriction fragments detected by single-copy probes are smaller than 200 kb for all of the rare-cutting restriction enzymes examined. Sizes of fragments detected by repetitive probes are variable, depending on the probes analyzed. By using PFGE, a tandemly repeated sequence, Os48, was found to be tightly linked to telomeric tandem repeats but not physically linked to r5s genes with which sequence homology had been observed. Relationships between genetic and physical distances have been established for three different chromosomal segments. In these regions 1 cm corresponds to ca. 260 kb on average. Analysis of a cluster of RFLP markers on chromosome 3 revealed that genetically clustered RFLP markers are also physically closely linked, suggesting that clustering of genetic markers may result in part from uneven distribution of single-copy sequences.

Chromosome Mapping↗
PubMed1993

Abundance, polymorphism and genetic mapping of microsatellites in rice.

Dinucleotide microsatellites have been characterized and used as genetic markers in rice. Screening of a rice genomic library with poly(dG-dA).(dC-dT) and poly(dG-dT).(dC-dA) probes indicated that (GA)n repeats occurred, on average, once every 225 kb and (GT)n repeats once every 480 kb. DNA sequencing of ten randomly selected microsatellites indicated that the numbers of repeats ranged from 12 to 34 and that the patterns of microsatellites in rice were similar to those of humans and other mammals. Primers to these microsatellite loci as well as to four published microsatellite-containing sequences have been designed and degrees of polymorphism has been examined with 20 rice accessions. Multiple alleles, ranging from 5 to 11, have been observed at all the microsatellite loci in 20 rice accessions. Alleles specific to two cultivated subspecies, indica and japonica, were found in some microsatellite loci. Heterozygosity values of all the microsatellite markers were significantly higher than those of RFLP markers, based upon a parallel comparison. Ten microsatellite loci have been genetically mapped to four rice chromosomes. The genomic distribution of microsatellites appears to be random in rice.

Base Sequence↗
PubMed1992

Genetic and physical analysis of the rice bacterial blight disease resistance locus, Xa21.

Nearly isogenic lines (NILs) of rice (Oryza sativa) differing at a locus conferring resistance to the pathogen Xanthomonas oryzae pv. oryzae were surveyed with 123 DNA markers and 985 random primers using restriction fragment length plymorphism (RFLP) and random amplified polymorphic DNA (RAPD) analysis. One chromosome 11 marker (RG103) detected polymorphism between the NILs that cosegregated with Xa21. All other chromosome 11 DNA markers tested were monomorphic between the NILs, localizing the Xa21 introgressed region to an 8.3 cM interval on chromosome 11. Furthermore, we identified two polymerase chain reaction (PCR) products (RAPD2148 and RAPD818) that detected polymorphisms between the NILs. Genomic sequences hybridizing with RAPD818, RAPD248 and RG103 were duplicated specifically in the Xa21 NIL. All three markers cosegregated with the resistance locus, Xa21, in a F2 population of 386 progeny. Based on the frequency with which we recovered polymorphic Xa21-linked markers, we estimated the physical size of the introgressed region to be approximately 800 kb. This estimation was supported by physical mapping (using pulsed field gel electrophoresis) of the sequences hybridizing with the three Xa21-linked DNA markers. The results showed that the three Xa21-linked markers are physically close to each other, with one copy of the RAPD818 sequences located within 60 kb of RAPD248 and the other copy within 270 kb of RG103. None of the enzymes tested generated a DNA fragment that hybridized with all three of the markers indicating that the introgressed region containing the resistance locus Xa21 is probably larger than 270 kb.

Chromosome Mapping↗
PubMed1988

Chromosomal locations of ten isozyme loci in rice (Oryza sativa L.) through trisomic analysis.

Chromosomal locations of 10 isozyme loci in rice (Oryza sativa L.) were determined through trisomic analysis. All 10 genes produced altered allozyme banding patterns in specific F1 trisomics. This served as the primary source of evidence for chromosome locations of Est-5, Icd-1, Acp-1, and Pgd-1. The locations of Amp-1, Amp-2, Amp-4, Pox-5, Got-1, and Cat-1 were further confirmed from segregation data in BC1 generations, as the ratios deviated significantly from 1:1 in the critical trisomics but agreed with the expected trisomic ratios. Triallelic heterozygotes were recovered for Amp-1 and Amp-2. On the basis of these data Got-1, Est-5, and Icd-1 were located to chromosome 1, Amp-1 to chromosome 2, Cat-1 and Pox-5 to chromosome 3, Acp-1 to chromosome 6, Amp-2 and Amp-4 to chromosome 8, and Pgd-1 to chromosome 11. Because Acp-2 and Pox-2 are known to be linked with Acp-1, they must also be on chromosome 6. The gene order and recombination values between isozyme loci on chromosomes 3, 6, 8, and 11 are presented.

Alleles↗
PubMed1984

Additional evidence for the augmented induction of tumor-specific resistance in vaccinia virus-primed mice by immunization with vaccinia virus-modulated syngeneic tumor cells.

The augmenting effect of vaccinia virus infection of tumor cells on induction of tumor-specific resistance was examined in mice. C3H/HeN mice were primed intraperitoneally (ip) with live vaccinia virus after whole-body irradiation with 250 rad of X-rays. Three weeks later the mice were immunized ip 3 times at weekly intervals with syngeneic murine hepatoma MH134 or spontaneous myeloma X5563 which had been infected in vitro with vaccinia virus and subsequently irradiated with 7000 rad of X-rays. One week after the third immunization, the mice were challenged with 1 X 10(5) viable cells of MH134 or X5563 ip or 1 X 10(6) tumor cells intradermally (id). On ip challenge with viable MH134 cells all mice that had not been pretreated died within 3 weeks due to ascites tumor out-growth, whereas all mice that had been vaccinia virus-primed and immunized with vaccinia virus-infected MH134 cells survived. On ip challenge with X5563 cells, the percentage survival of vaccinia virus-primed and vaccinia virus-modified tumor-immunized mice was 80%. On id challenge with MH134 and X5563 tumor cells, in un-treated mice tumors grew to more than 5 mm in diameter within 3 weeks, whereas 90% and 60%, respectively, of the mice that had been vaccinia virus-primed and immunized with vaccinia virus-infected tumor cells showed no tumor out-growth. Pretreatment by only immunization with vaccinia virus-infected cells or vaccinia virus-priming and immunization with virus non-infected tumor cells were not effective for preventing induction of tumor-resistance to either ip or id challenge with MH134 or X5563 tumor cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Prevention of syngeneic tumor growth in vaccinia virus-primed mice by immunization with vaccinia virus-modulated tumor cells.

Immunization with vaccinia virus-infected and then X-ray-irradiated murine hepatoma MH134 cells provided C3H/He mice with strong resistance to challenge with viable MH134 cells. Male C3H/He mice of 5 to 6 weeks old were primed intraperitoneally (IP) with 1 x 10(7) PFU of live vaccinia virus (Ikeda strain) after irradiation with 250 R of X-ray. Three weeks after priming, the mice were immunized IP 3 times at weekly intervals with 1 x 10(7) X-ray-irradiated MH134 cells that had been infected with vaccinia virus 8 h before irradiation. Over 60% of these cells showed vaccinia virus-induced antigen on their surface (membrane antigen). Challenge with viable MH134 cells was done by inoculating 1 x 10(5) cells IP one week after immunization. During a 4-week observation period, all the untreated control mice died with ascites. On the contrary, all the mice that were X-ray-irradiated, primed and immunized survived challenge with the tumor cells for at least 4 weeks. The mortalities of mice in other groups that were not irradiated, or not primed, or immunized with only X-ray-irradiated tumor cells, were at lowest 50%.

Animals↗