NUCLEAR BEHAVIOR IN THE BASIDIUM OF FOMES ANNOSUS

Meiotic division in Fomes annosus is similar to that reported for other higher fungi. Nuclei in dikaryotic cells prior to fusion in the basidia are long, thin, and double-stranded with paired heterochromatic areas. Various stages of prophase are similar to those in higher plants. At metaphase I and II seven pairs of chromosomes are aligned in a circle and the chromatids migrate to opposite poles established by two centrioles. The centrioles function in the movement of the nuclei in the basidium, nuclear alignment prior to fusion, establishment of poles for division, and the migration of the nuclei into the basidiospore. After nuclei migrate into the basidiospore, they soon divide, producing a binucleate spore.     

NUCLEAR BEHAVIOR IN THE VEGETATIVE HYPHAE OF CERATOCYSTIS FAGACEARUM

Vegetative nuclear division in Ceratocystis fagacearum (Bretz) Hunt was found to differ from classical mitosis in that: (1) division always occurs perpendicular to the longitudinal axis of the cell, (2) anaphase movement is unilateral and unsynchronized, (3) a spindle occurs only between separating chromatids. Interphase and prophase nuclei and nucleoli are morphologically similar to those in higher plants. At metaphase the associated chromosomes form a bar of chromatin and lie against the hyphal wall. Spindle fibers appear between separating chromatids, perhaps pushing them apart. When nuclear division is complete the nuclei become attenuated and migrate. Vegetative nuclear division in C. fagacearum may be an evolutionary form of classical mitosis.     

NUCLEAR BEHAVIOR IN THE BASIDIOMYCETE,VOLVARIELLA VOLVACEA

The basidiospores of the straw mushroom are typically uninucleate and its vegetative hyphae are generally multinucleate. There is a marked reduction of nuclear number in the trama and subhymenium. Interphase nuclei exist in two forms, each of which undertakes a particular mode of division. The “diffused” nuclei divide by conventional mitosis while the “constricted” ones divide amitotically. In metaphase of mitosis nine chromosomes were seen both in polar and lateral view. This haploid number confirms the nine bivalents found in basidia during meiosis. A unique characteristic of this fungus is that the diploid nucleus, the two postkaryotic nuclei and the four postkaryotic nuclei may be enclosed by a well-defined nuclear envelope during division.     

THE GENETIC CONTROL OF PATHOGENICITY,SEROTYPES AND VARIABILITY IN PUCCINIA SORGHI

Flangas , A. L., and J. G. Dickson . (U. Wisconsin, Madison.) The genetic control of pathogenicity, serotypes and variability in Puccinia sorghi. Amer. Jour. Bot. 48(4): 275–285. Illus. 1961.—Four urediospore clones of P. sorghi were inbred through the alternate host, Oxalis, and the recombinant lines were compared with the mother clones for changes in pathogenicity and serological reaction. The aecial, inbred recombinant lines were scored for pathogenicity on 6 inbred lines of maize, 4 of which contained single, dominant alleles isolated from a single gene locus each conditioning differential rust reaction and Pop 35 and Pop 36, each with 2 recessive genes. The inbred, recombinant lines from each of the 4 mother clones reflected similar dimensional changes from original pathogenicity, that is, an ultimate gain or loss in host range or specificity. Based on reaction type incited on the 4 allelic differential hosts, continued inbreeding through 3 generations did not segregate homozygous pathogenic complements into distinct pathogenic biotypes. A similar array of pathogenic types was produced after each generation of inbreeding. The suppressed pathogenicity types in the dicaryotic line were revealed only through recombination. Hybridization between dicaryotic lines of selected pathogenic types of sibling and nonsibling pedigree confirmed the indeterminate nature of the pathogenic locus. The genetic basis of the commonly occurring mesothetic-X reaction (necrotic flecks and uredia of varying size surrounded by chlorotic and necrotic areas) is explained by the heterologous complementarity of fit of the interacting genic systems (genetic units). The heterologous mesothetic-X reactions offer ambiguous definition to the specificity state of the interaction and cannot be explained on the discrete gene-for-gene basis of rust reaction. Antisera produced from the pathogenic types differentiated the homologous from the heterologous combinations and revealed cross-reactions with P. graminis avenae. The comparative antigen constitution of the urediospore clones and the sibling recombinants thus far reveal a possible parallel existing between the modes of inheritance of pathogenic specificity and antigenic specificity.     

中国百合目植物柄锈菌属的种

本文报告了寄生在中国百合目植物(薯祯科,鸢尾科,灯心草科和百合科)上的柄锈菌共2I种。其中有2个新种,它们是刘氏柄锈(Puccinia lioui J.Y. Zhuang sp. nov.)和胀柄柄锈(Puccinia oedopoda J.Y. Zhuang sp. nov.),均寄生在菝葜属(Smilax)植物上。每个种都作了详细描述并附图。对百合科植物上的种附加了检索表。本文所引证的标本均保藏在中国科学院微生物研究所真菌标本室。     

NUCLEAR STRUCTURE AND DIVISION IN THE VEGETATIVE MYCELIUM OF THE SAPROLEGNIACEAE

Bakerspigel , Alexander . (The New Mount Sinai Hospital, Toronto.) Nuclear structure and division in the vegetative mycelium of the Saprolegniaceae. Amer. Jour. Bot. 47(2): 94—100. Illus. 1960.–Saprolegnia parasitica, S. ferax and Achlya racemosa are additional examples of fungi in whose vegetative mycelium the nuclei do not divide in a manner directly comparable to ordinary mitosis. During division the entire nucleus, which consists of a crescent, ring or cap of chromatin and the nucleolus, becomes angular and elongates. The chromatin separates into 2 portions which are situated at opposite ends of the elongating nucleus. As division proceeds the elongated nucleus constricts at the midregion and the sister nuclei separate. Each sister nucleus consists of a crescent of chromatin and a portion of the divided nucleolus. Spindles, chromosomal filaments or metaphase plates could not be demonstrated during division.     

THE SYNTHESIS OF PHOSPHOLIPIDS IN THE NUCLEUS AND NUCLEAR MEMBRANE OF SYNCHRONIZED HeLa CELLS

HeLa cells were synchronized by a double thymidine block and pulse labeled at different stages of the cell cycle with ³H-choline. The specific activity of phospholipids extracted from the cell, the nucleus and the nuclear membrane showed a progressive increase from S to G₁; the incorporation of choline into phospholipids of asynchronous cells showed a specific activity intermediate between the values of S and G₁ cells. Similar results were obtained when ³²phosphorus was used as a precursor instead of choline. Thin layer chromatographic analysis of phospholipids extracted from cells in S and from cells in G₁ failed to show any difference in the distribution of radioactivity among the various phospholipid classes. Choline uptake by HeLa cells in different phases of the cell cycle did not show significant variations. However, during the synchronization process, shortly after the addition of excess thymidine, an increased uptake of choline by cells and an increased incorporation of choline into phospholipids were found. The results indicate that some of the changes occurring in phospholipids synthesis may not be cell cycle dependent, but may be the effect of the synchronizing process.