Genetic variation detected with random amplified polymorphicDNA markers among isolates of the red rot disease fungus Pythiumporphyrae isolated from Porphyra yezoensis from Koreaand Japan

ABSTRACT:   Genetic variation of the fungal parasite Pythium porphyrae ,causative organism of red rot disease of Porphyra , isolatedfrom Asan, Mokpo, Pusan and Wando in Korea, and from Aichi, Fukuokaand Miyagi in Japan was investigated by random amplified polymorphicDNA (RAPD) cluster analysis. The total 67 RAPD markers were generatedfrom 38 isolates by RAPD-polymerase chain reaction (PCR) using arbitraryprimers consisting of 10 nucleotide sequences and 33 of them indicatedpolymorphisms. The dissimilarity coefficients calculated from theRAPD banding patterns ranged from 0.0010 to 0.6983. The dendrogramgenerated by the unweighted pair-group method using arithmetic averagesshowed that the 38 isolates were classified into three clusters(Groups 1, 2 and 3). Group 1 consisting of two isolates from Miyagiwas separated from all other isolates by a genetic distance of 0.6983.Groups 2 and 3 containing the majority of the isolates were branchedon genetic distance of 0.3957. These two clusters subdivided intofour and three subclusters, respectively, which were apparentlyassociated with geographic origins of the isolates. Interestingly,the isolates from Asan of Korea were close to Japanese isolatesrather than Korean isolates on genetic diversity. In addition, thegenetic distances of intra-isolates from Japan were higher thanthose from Korea.     

COMPUTED TOMOGRAPHIC APPEARANCE OF PRIMARY LUNG TUMORS IN DOGS

Canine primary lung tumors typically appear radiographically as a well‐circumscribed solitary mass in the periphery of a caudal lung lobe. Consolidated and diffuse forms of primary lung tumors have also been described. Nineteen dogs with computed tomographic (CT) images of the thorax and a histological diagnosis of primary lung tumor (17 primary carcinomas and two primary sarcomas) were evaluated retrospectively to characterize the CT findings. All primary lung tumors were bronchocentric in origin with internal air bronchograms. The bronchi were typically narrowed, displaced, and often obstructed by the tumor. Eighteen of 19 (95%) of the tumors were solitary and there was one pneumonic/alveolar form. Most solitary tumors were well circumscribed (17/18), located in the central to periphery of the lung (14/18), and in a cranial or caudal lobe (16/19). Most primary lung tumors (11/17) had mild to moderate heterogeneous contrast enhancement. Five of 19 dogs (26%) had evidence of pulmonary metastasis. Internal mineralization (3/19) and tracheobronchial lymphadenopathy (4/19) were also identified. On CT examination, solitary, well circumscribed, bronchocentric masses with internal air bronchograms are consistent with a primary pulmonary tumor in dogs.     

SLA typing using the PCR‐SSP method and establishment of the SLA homozygote line in pedigreed SNU miniature pigs

Seoul National University (SNU) miniature pigs represent a closed colony with 24 founder pigs and a well preserved pedigree. Characterization using mRNA sequence analysis was conducted for 6 swine leukocyte antigen (SLA) loci in parental or founder pigs, and 17 defined alleles were detected. Based on these complete coding sequences, 17 sequence specific primers (SSPs) were designed for polymorphic sites. To validate the specificity of each allele SSP, the PCR‐SSP was conducted with defined allele clones as templates. PCR‐SSP was conducted with the hot start polymerase and touch‐down PCR. The parental or found SNU miniature pigs showed overall SLA class I and II heterozygotes. Using the established PCR‐SSP method, we conducted SLA typing for breeding stock including 2 pedigreed pigs and identified the novel SLA class II homozygote haplotye (DRA*0201, DRB1*0403, DQA*0102 and DQB1*0701) and 2 SLA homozygote pig lines: SLA class I Hp‐3.0 and class II Hp‐0.3, and SLA class I Hp‐2.0 and class II Hp‐0.2. We thought that our PCR‐SSP SLA typing method could be applicable for new SLA homozygote line establishment by assignment and scheduled breeding.     

Phylogenetic analysis for the Seoul National University (Minnesota) miniature pig by mitochondrial DNA sequence polymorphism

Seoul National University (SNU) miniature pigs are originated from the Minnesota miniature pig. This study was conducted to investigate the maternal origin of SNU (Minnesota) miniature pigs and their phylogenetic relationships by analyzing the mitochondrial DNA (mtDNA) D‐loop (control region) sequence. Two mtDNA D‐loop sequences of the SNU miniature pigs were identified. On an unweighted pair‐group method with an arithmetic mean (UPGMA) phylogenetic tree analysis, the large white was the pig breed closest to the SNU miniature pig, and the pairwise distance analysis showed the same result. While mtDNA sequences of 4 pig breeds which were used to establish Minnesota miniature pig were not known, our result might be different from the history of the Minnesota miniature pig development. In conclusion, we thought that some haplotypes of the Minnesota miniature pig maternally were originated from the Large white pig, or that wild pigs had similar mtDNA sequences to the Large white pig, and all SNU miniature pigs were derived from this colony.     

Ultrastructural analysis of responses of host and fungal cells during plant infection

Cellular responses in fungi and in susceptible or resistant hosts during fungus–plant interactions have been studied ultrastructurally to examine their role in pathogenicity. Pathogenicity is determined in some saprophytic fungi by various factors: the production of disease determinants such as the production of host-specific toxins (HSTs) or the extracellular matrix (ECM) by fungal infection structures and H₂O₂ generation from penetration pegs. Three different target sites for HSTs have been identified in host cells in many ultrastructural studies: plasma membranes, chloroplasts, and mitochondria. The mode of action of HSTs is characterized by the partial destruction of the target structures only in susceptible genotypes of host plants, with the result that the fungus can colonize the host. The infection structures of most fungal pathogen secrete ECM on plant surfaces during fungal differentiation, while the penetration pegs of some pathogens produce reactive oxygen species (ROS) in the cell walls and plasma membranes. The pathological roles of ECM and H₂O₂ generation are discussed here in light of ultrastructural evidence. Host and fungal characteristics in the incompatible interactions include the rapid formation of lignin in host epidermal cell walls, failure of penetration pegs to invade lignin-fortified pectin layers, the inhibition of subcuticular hyphal proliferation and the collapse of hyphae that have degraded cell walls within pectin layers of the host. Apoptosis-like host resistant mechanism is also discussed.     

Evaluation of rice allelopathy in hydroponics

The inhibitory activity of water extracts from the shoots and roots of three rice cultivars, Taichung native 1 (TN1) and IAC165 (both allelopathic rice) and AUS196 (non-allelopathic rice), grown in hydroponics was evaluated. The release of germination inhibitors by allelopathic rice plants into hydroponic solution was also determined with freshly collected solution and XAD-4 resin desorbate. The degree of the inhibition was quantified in terms of root growth in Echinochloa colona, Echinochloa crus-galli, Echinochloa crus-galli var. oryzicola, Triantema portulacastrum and Lactuca sativa. The allelopathic activity of rice was species specific, and depended on source and concentration. Root length of all test species was inhibited by the different concentrations of shoot extract of allelopathic and non-allelopathic rice. However, of the three cultivars, TN1 showed higher inhibition than IAC165 and AUS196 in all test species. Water extracts of shoots and roots significantly inhibited root growth in E. crus-galli but the shoot extract gave a greater inhibitory effect on E. crus-galli than the root extract. Root exudate of TN1 inhibited root elongation of E. crus-galli from 2 weeks after transplanting (WAT) and the inhibition continued for 4 WAT. The results confirmed the previous finding of a laboratory bioassay that the TN1 had allelopathic activity and produced allelochemicals that inhibit growth of some weed species.