APOLAR EMBRYOS OF FUCUS RESULTING FROM OSMOTIC AND CHEMICAL TREATMENT

Embryos of the brown alga Fucus vesiculosas L. were grown as populations in glass petri dishes in seawater at 15 C in continuous low-intensity unilateral fluorescent illumination for periods up to 2 weeks. A quantitative estimate of increase in nuclear number was made from acetocarmine squash preparations of samples taken at 12-or-24 hr intervals. Over the period of 2-6 days embryos showed a doubling time of about 12-18 hr. Under normal seawater culture conditions each embryo formed a single rhizoid. When grown in seawater supplemented with sugar concentrations above 0.4 m , Fucus embryos developed as multicellular spherical embryos lacking rhizoids. In 0.6 m sucrose-seawater, 97% of the embryos were apolar at 2 days; only 37% were apolar at 4 days, many having recovered from the sucrose inhibition. Some embryos remained apolar after growth in 0.6 m sucrose for 2 weeks. Nuclear counts showed that sucrose-seawater markedly inhibited the rate of cell division. Other sugars including D-glucose, D-fructose, D-galactose and the sugar alcohol D-mannitol were also effective. When apolar embryos grown in sucrose-seawater were returned to seawater, embryo growth resumed at the normal seawater rate, judged from nuclear counts. Such embryos formed multiple rhizoids, varying from two to eight rhizoids per embryo, which developed on the embryo quadrant or half away from the unilateral light. Each of the multiple rhizoids originated from a single small cell in the periphery of the multicellular spherica embryo. Thus the rhizoid-forming stimulus apparently had been subdivided among a number of the cells of the apolar embryos. The implications of this finding are discussed. Attempts to produce multiple rhizoids by treatment of embryos with indoleacetic acid or 2,4-dichlorophen-oxyacetic acid failed. However, embryos treated with 10⁻⁴ M or 5 × 10⁻⁵ m 2,3,5-triiodobenzoic acid formed 40 and 30% multiple rhizoids, respectively, suggesting that some chemical, perhaps hormonal, mechanism is involved in polarization and rhizoid initiation in Fucus embryogenesis.     

Clone bank and physical and genetic map of potato chloroplast DNA

Summary Clone banks of PvuII, BamHI and XhoI fragments were generated of the Solanum tuberosum cv Katahdin plastome. These clone banks, in conjunction with molecular hybridization to tobacco ctDNA probes, were used to construct a physical map of potato ctDNA. The potato plastome was found to be a circular molecule of 155–156 Kbp containing two inverted repeat regions of 23–27 Kbp. The arrangement of restriction sites is very similar to that of other Solanaceae plastomes. Heterologous hybridization to known ctDNA encoded gene probes from tobacco allowed us to establish a genetic map of the potato chloroplast genome. The arrangement of these genes on the potato plastome resembles that on most higher plant ctDNAs.     

Production of carotene stereoisomers by Phycomyces blakesleeanus

Summary -Carotene steroisomers, mainly all-trans and to a small extent 9-cis, may be produced by the fungus Phycomyces blakesleeanus under normal fermentation conditions. The amount of the 9-cis--carotene may comprise up to 15% of the total -carotene. Similarly, cis-lycopene or-phytoene stereoisomers may be obtained when the fungus is fermented in the presence of specific -carotene inhibitors such as nicotine or diphenylamine respectively. This is the first report on the occurrence of cis-stereoisomers of carotenes in mycelial fungi.     

Adenosine deaminase activity in relation to the appearance of early and late Epstein-Barr virus antigens induced in lymphoblastoid cells

Summary Induction of Epstein-Barr virus (EBV) capsid antigen synthesis in 59.6% of P3HR-1 cells was followed by a decrease to 70% in adenosine deaminase (ADA) activity. In Daudi cells synthesizing EBV early antigen, ADA activity did not decrease.     

Complementation in Nonconidiating Mutants of Trichoderma

Nonconidiating (Con(-)) mutants were isolated from wild-type and color mutants of the fungus Trichoderma viride Pers. ex Fries. Heterokaryons were easily produced and maintained, and the complementation relationships among the Con(-) mutants were established. Most Con(-) mutants could complement one or more of the other Con(-) mutants. When marked Con(-) mutants were mixed with marked Con(+) testers, conidiating heterokaryons were formed. The conidia thus obtained produced only the parental type colonies after replating, indicating that nonconidiation is a nuclear characteristic. Allowing two Con(-) colonies to meet and produce a heterokaryon, it was found that the migration of nuclei reached a rate of 5 mm per hr, which is several times greater than the rate of hyphal elongation; it was also found that heterokaryosis of a mycelial region preceded its ability to conidiate.     

Study of the inheritance of sex expression in the cucumber. The interaction of major genes with modifying genetic and non-genetic factors

Summary Two major genes and a complex of polygenes affecting sex expression inCucumis sativus L. as well as their interaction with some nongenetic factors were investigated in the present study. The genetic factorst was found to affect sex by inducing a shift of the predetermined flowering pattern of this plant, in the direction of its base. As this pattern is composed of a staminate stage followed by a mixed (staminate-pistillate) stage and a pistillate stage, a double dose ofst will induce a change from the normal monoecious sex expression (to absolute gynoecism.The second major gene studied,m, known previously to control sex in the individual flower (m/m—andromonoecious,M—monoecious), also interacts with factors affecting the flowering pattern by inducing male tendency.Using an ordinary commercial monoecious stock additional modifying factors for sex expression were demonstrated, by eight generations of selection for high (in male direction) and for low (in female direction) node number to the first pistillate flower. A comparison of the means and frequency distributions of node number of the two selected lines, their F₁ and F₂, indicated polygenic control of this character.It was found that two non-genetic factors, day length and gibberellic acid (GA), may mimic the genetic factors for sex expression. Furthermore, evidence was presented, indicating that this sex controlling ability of GA and the modifying genes may be based on physiological conditions common to those two genetic and nongenetic factors.The overall mechanism of sex control in the cucumber and in other plants was discussed and a hypothetic model for the evolution of dioecism in flowering plants was proposed.     

Purification and Characterization of the Voltage-Dependent Anion-Selective Channel Protein from Wheat Mitochondrial Membranes

An approximately 29-kD protein was purified from the membrane fraction of wheat (Triticum aestivum cv Dganit) mitochondria by the utilization of standard liquid chromatography techniques. The protein, designated MmP29 for mitochondrial membrane protein having a molecular mass of approximately 29 kD, exhibited cationic properties in a buffering solution, adjusted to pH 7.5. This positive charge enabled its passage through a diethylaminoethyl column, without interaction with the positively charged matrix. Subsequently, this protein was separated from the remaining polypeptides by a preferential elution from a hydroxylapatite/celite mixed column. Reconstituted liposomes containing this protein were characterized as being permeable to 8-amino-naphthalene 1,3,6-trisulfonic acid disodium salt (Mr 445) but non-permeable to dextran fluorescein (Mr 40,000). Additionally, MmP29 was inserted into planar phospholipid membranes, and anion-selective, voltage-dependent channels were demonstrated. All of the MmP29 properties mentioned highly resemble voltagedependent, anion-selective channel (VDAC) proteins, suggesting that MmP29 is the mitochondrial outer membrane VDAC protein of wheat.