GENETIC CONTROL OF CONIDIATION IN ASPERGILLUS RUGULOSUS

The potential for the production of abundant conidia was suggested when an essentially non-conidial isolate of Aspergillus rugulosus, obtained from dune sand, was grown at 25 C rather than at the usual 37 C. Ultraviolet-light-induced conidial strains were obtained from the original non-conidial isolate. Evidence is presented which suggests that the production of conidia is under the control of a single nuclear gene. The data, with a single exception, suggest that induced conidial mutations represent alterations at the same locus. Crosses with isolates from various localities indicate that the genes controlling conidiation in these strains may be linked to or independent of the genes studied in the original dune-sand isolate. No evidence has been obtained which would suggest involvement of a diffusible substance in the control of conidiation.     

GENETIC CONTROL OF VERY EARLY MAMMALIAN DEVELOPMENT

The overall picture of mammalian preimplantation development is one of complex but integrated molecular activity. As development progresses from the 1 cell stage, blastomeres acquire properties that differ from those of cells of previous stages and eventually differ from one another even at the same stage. The evidence concerning the role of the embryonic genome during this process can be summarized under two headings:
(1) Expression of embryonic genome
(a) Quantitative and qualitative changes in RNA and protein synthesis begin to occur soon after fertilization.
(b) Changes in structural proteins (enzyme activities, transport systems and intercellular junctions) occur throughout early development.
(c) Paternal gene products can be detected as early as the 2-cell stage.
(2) The need for expression of the embryonic genome
(a) Inhibitors of RNA and protein synthesis result in abnormal and lethal development.
(b) Several mutations ( T/t, A^y, Os, c^25H, Om, Ts ) are lethal during early development.
(c) Chromosomal imbalance (monsomy, haploidy, nullisomy) has adverse effects on early development.
Even though studies in vitro on the inhibition of translation indicate that stable maternal messenger RNAs are present in the developing mouse embryo, the evidence outlined in this article strongly supports the belief that embryonic gene expression occurs very early in development (at least by the 2 cell stage) and that this expression is required for normal development.     

CYTODIFFERENTIATION IN THE ROSY MUTANT OF DROSOPHILA MELANOGASTER

In the rosy mutant of Drosophila melanogaster, two types of autofluorescent cytoplasmic inclusions are found in the cells of the posterior region of the fatbody at the prepupal stage. Bright yellow autofluorescent granules accumulating within larger inclusions clearly demarcate this area of the fatbody which also contains cobalt blue fluorescent globular material. Such inclusions were not noted in the normal Ore-R strain at this stage nor in the series of mutant strains examined other than the rosy² and maroon-like mutants. The pattern of biochemical deviation of the latter two mutants is known to be identical to that of the rosy mutant, and a portion of this mutant upset can be ascribed to the absence of xanthine dehydrogenase. These mutants lack the products of enzyme activity, uric acid and isoxanthopterin, and accumulate their precursors, hypoxanthine and 2-amino-4-hydroxypteridine. Chromatographic studies on the fatbody of rosy prepupae have shown that 2-amino-4-hydroxypteridine is limited to the posterior region; this correspondence in location as well as color of fluorescence indicates that the cobalt blue auto fluorescent globules in the fatbody contain 2-amino-4-hydroxypteridine. In the normal strain, isoxanthopterin was identified in the chromatograms of the posterior region of the fatbody, but it was not obtained from the anterior region of the fatbody. On the other hand, xanthine dehydrogenase activity could be demonstrated throughout the fatbody of the normal strain. The restriction of isoxanthopterin to a certain group of fat cells in the wild type strain and its absence from other fat cells can be explained by the differential distribution of its immediate precursor, 2-amino-4-hydroxypteridine, as displayed in the mutant rosy.     

ESTROGEN-INDUCED CYTODIFFERENTIATION OF THE OVALBUMIN-SECRETING GLANDS OF THE CHICK OVIDUCT

The histological, ultrastructural, and biochemical changes occurring during hormone-induced cytodifferentiation of the ovalbumin-secreting glands in the chick oviduct have been studied. Marked perivascular edema is an initial response of the immature oviduct stroma to diethylstilbestrol administration and is accompanied by an interstitial migration of mononuclear cells. Mitotic activity in the immature mucosal epithelium increases within 24 hr, and glands begin to develop on days 2–4 as budlike invaginations into the subepithelial stroma. An immediate intracellular effect of the hormone is aggregation of previously dispersed ribosomes. Ribosomal zones in the nucleolus gain prominence, and there is a progressive development of rough endoplasmic reticulum in the epithelial cells. Extensive profiles of endoplasmic reticulum are present in the gland cells by day 6. Fine apical progranules appear in the epithelial cells on day 2, and ovalbumin can be measured immunochemically by day 3 at about the same time that new species of nuclear RNA have been identified. Ovalbumin granules form within condensing vacuoles in the Golgi zone and begin to be released into the lumina of the gland acini at about day 6 of the treatment.     

COSTS AND BENEFITS OF MOSQUITO REFRACTORINESS TO MALARIA PARASITES: IMPLICATIONS FOR GENETIC VARIABILITY OF MOSQUITOES AND GENETIC CONTROL OF MALARIA

The problem of fitness costs associated with host resistance to parasitism is related to the evolution of parasite virulence, population genetic diversity and the dynamics of host-parasite relationships, and proposed strategies for disease control through the genetic manipulation of mosquito vectors. Two Aedes aegypti populations, refractory and susceptible to Plasmodium gallinaceum, were previously selected from the Moyo-In-Dry strain (MOYO) through inbreeding (F = 0.5). Reproductive success and survivorship of the two populations were compared, and the influence of the parasite on mosquito fitness also was evaluated. Fitness components studied include fecundity, adult survivorship and egg-to-adult developmental time, blood-meal size, and adult body size. The refractory population has a significantly shorter egg-to-adult developmental time and a smaller body size, takes a smaller blood meal, and subsequently lays fewer eggs than the susceptible population. The mean longevity of the refractory population is significantly shorter than the susceptible population. Exposure to the parasite exhibited little effect on the survivorship and fecundity of either population. Several factors may contribute to the lower fitness of the refractory population, including founder effect, inbreeding depression, the effect of other uncharacterized genes linked to genes conferring refractoriness, and pleiotropic effects associated with these genes. The results are discussed in relation to the genetic diversity of natural mosquito populations and their implications for the genetic control of malaria.     

STUDIES ON THE GENETIC CONTROL OF RESISTANT SPORANGIUM FORMATION IN ALLOMYCES

The diploid sporophyte of the phycomycetous fungus Allomyces arbuscula bears two types of sporangia: thin-walled, colorless, ephemeral zoosporangia (ZS) and thick-walled, dark-brown, resistant sporangia (RS). Normal wild-type cultures (strain Portugal IE) under standard conditions produce approximately 90% of their total sporangia as RS. These RS give the cultures a dark-brown color. A mutant was induced with UV irradiation in which the ratio of ZS to RS was shifted so that only 20% of the total sporangia are RS. These cultures are a pale, tan color. Hybrids between the mutants and wild-types produce ca. 65% RS and are also intermediate in the color of the culture. Meiotic segregation in the RS of the hybrid sporophytes gives gametophytes half of which when selfed produce mutant sporophytes and half of which produce wild-type sporophytes. The shift from RS to ZS formation is thus considered to be the result of a one-gene mutation at a locus ‘R.’ The haploid gametophytes of wild-type strains have in addition to male and female gametangia a small number (2-4%) of RS. In mutant gametophytes the percent RS has dropped to 0.1-0.2%. The proposed genotypes at the ‘R’ locus in Allomyces arbuscula are: wild-type sporophytes (RR), hybrid sporophytes (Rr), mutant sporophytes (rr), wild-type gametophytes (R) and mutant gametophytes (r).     

植物细胞的遗传全能性与组织培养形态发生控制

引言自1902年德国植物学家Haberlandt提出植物的单个细胞可能具有分化的全能性的理论以来,人们才开始从事植物组织培养,以致今天广泛用来有意识地定向控制遗传变异和人工创造植物新类型的研究。到今据不完全统计,全世界约有1000种高等植物作过离体培养尝试。根据大量实验结果证明,植物单个细胞具有遗传的全能性,     

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.     

GENETIC AND ENVIRONMENTAL CONTROL OF GLYCOLIC ACID OXIDASE ACTIVITY IN ECOTYPIC POPULATIONS OF TYPHA LATIFOLIA

Glycolic acid oxidase activity at 25 C in leaf homogenates of ecotypic populations of Typha latifolia varied according to native climate of the population and current growing conditions. Activity of plants grown under warm/short day conditions was positively correlated with maximum summer temperature at the site of population origin. Activity of plants grown under cool/ long day conditions was negatively correlated with length of growing season at the site of origin. Populations from sites characterized by a long growing season are much less susceptible to environmental regulation of enzymic level than populations originating in short growing season sites. Enzyme activity is not a secondary reflection of differentiation at the level of chlorophyll or cofactor concentration. Enzymic differences between ecotypic populations reflect differences in control systems at the level of protein synthesis and genetic structure.     

ENVIRONMENTAL AND GENETIC CONTROL OF BRAIN AND SONG STRUCTURE IN THE ZEBRA FINCH

Birdsong is a classic example of a learned trait with cultural inheritance, with selection acting on trait expression. To understand how song responds to selection, it is vital to determine the extent to which variation in song learning and neuroanatomy is attributable to genetic variation, environmental conditions, or their interactions. Using a partial cross fostering design with an experimental stressor, we quantified the heritability of song structure and key brain nuclei in the song control system of the zebra finch and the genotype‐by‐environment (G × E) interactions. Neuroanatomy and song structure both showed low levels of heritability and are unlikely to be under selection as indicators of genetic quality. HVC, in particular, was almost entirely under environmental control. G × E interaction was important for brain development and may provide a mechanism by which additive genetic variation is maintained, which in turn may promote sexual selection through female choice. Our study suggests that selection may act on the genes determining vocal learning, rather than directly on the underlying neuroanatomy, and emphasizes the fundamental importance of environmental conditions for vocal learning and neural development in songbirds.     

GENETIC CONTROL OF MITOCHONDRIAL THYMIDINE KINASE IN HUMAN-MOUSE AND MONKEY-MOUSE SOMATIC CELL HYBRIDS

Distinctive thymidine (dT) kinase molecular forms are present in mouse, human, and monkey mitochondria. Disk polyacrylamide gel electrophoresis (disk PAGE) analyses have shown that the mitochondrial-specific dT kinases differ from cytosol dT kinases in relative electrophoretic mobilities (Rm). Furthermore, the mouse mitochondrial dT kinase differs in Rm value from primate mitochondrial dT kinases. The mouse and primate cytosol dT kinases can also be distinguished. Disk PAGE analyses have been carried out on the cytosol and mitochondrial dT kinases of human-mouse (WIL-8) and monkey-mouse (mK·CV^III) somatic cell hybrids in order to learn whether the mitochondria of the hybrid cells contained murine mitochondrial-specific, primate mitochondrial-specific, or both dT kinases. WIL-8 cells were derived from cytosol dT kinase-negative, mitochondrial dT kinase-positive mouse fibro blasts and from cytosol dT kinase-positive, mitochondrial dT kinase-positive human embryonic lung cells; they contained mostly mouse chromosomes and a few human chromosomes, including the determinant for human cytosol dT kinase. The mK·CV^III cells were derived from cytosol dT kinase-negative, mitochondrial dT kinase-positive mouse kidney cells and from cytosol dT kinase-positive, mitochondrial dT kinase-positive monkey kidney cells; they contained mostly mouse chromosomes and a few monkey chromosomes, including the determinant for monkey cytosol dT kinase. Disk PAGE analyses demonstrated that the mitochondria of human-mouse and monkey-mouse somatic cell hybrids contained the mouse-specific mitochondrial dT kinase but not the human- or monkey-specific mitochondrial dT kinase. These findings suggest that primate cytosol and mitochondrial thymidine kinase genes are coded on different chromosomes.     

松江鲈线粒体DNA控制区结构和遗传多样性分析

为探讨松江鲈(Trachidermus fasciatus Heckel)线粒体控制区特征及其群体遗传结构, 研究测定分析了中国和日本沿海共8个群体的线粒体控制区序列, 分析了其结构特征, 识别出终止序列区(ETAS)、中央保守区(CD)和保守序列区(CSB)的特征序列。遗传多样性分析结果显示: 69个松江鲈个体共检测到47个单倍型, 呈现出核苷酸多样性(0.0079)较低和单倍型多样性(0.978)较高的特点。单倍型邻接关系树和单倍型网络关系图均显示松江鲈分为中国和日本两大世系。遗传分化系数(Fst)和分子方差分析(AMOVA)结果表明, 松江鲈中国群体和日本群体之间存在的遗传差异较显著, 中国沿海各群体之间亦存在着一定程度的遗传差异, 该分化主要由历史环境变动、当代环境因素和自身生态习性等原因造成。     

基于线粒体控制区的中华绒螯蟹群体遗传多样性分析

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