Genetic control of the mitochondrial form of superoxide dismutase in hexaploid wheat

Extracts of mature grains of a large number of aneuploid derivatives of Triticum aestivum cv. Chinese Spring and of the members of five wheat-alien chromosome addition series were subjected to isoelectric focusing in polyacrylamide gels in order to study the genetic control of superoxide dismutase (SOD). Evidence was obtained that homologous structural genes for the mitochondrial form of SOD are located in the long arms of the homoeologous group 2 chromosomes of Chinese Spring and in chromosome 2R of Secale cereale cv. Imperial. The SOD gene loci located in chromosomes 2A, 2B, 2D, and 2R were designated Sod-A1, Sod-B1, Sod-D1, and Sod-R1, respectively. Chromosome-arm pairing data indicate that 2DL is not homoeologous to either 2AS or 2BL. The results of this study suggest, however, that 2BL is partially homoeologous to both 2AL and 2DL.Technical article No. 21074 of the Texas Agricultural Experiment Station. This work was supported by USDA Grant 83-CRCR-1-1322 to GEH.     

Catabolism of myo-Inositol to Precursors Utilized for De Novo Glycerolipid Biosynthesis

Systemic injection of [2-3H]myo-inositol into frogs resulted in the incorporation of more than half of the label into glycerolipid classes other than phosphoinositides in retinal rod outer segment membranes. Following methanolysis and differential extraction of isolated lipid classes, radioactivity was recovered primarily in the aqueous phase. After phospholipase C hydrolysis of the total membrane lipids, 97% of the radioactivity was extractable with organic solvents, and 70% of the label in lipids was in 1,2-diglycerides. These results indicate that the label was incorporated primarily into the glyceryl moiety of the membrane glycerolipids. Intraocular injection of frog eyes or in vitro incubation of frog retinas with [2-3H]myo-inositol resulted in the incorporation of radioactivity almost exclusively into phosphoinositides in rod outer segment membranes. Incubation of retinas with [U-14C]glucuronic acid did not result in the formation of labeled retinal lipids. These results suggest that myo-inositol can be catabolized systemically to precursors utilized for glycerolipid biosynthesis in the retina.     

Cloning and Characterization of Yeast LEU4, One of Two Genes Responsible for α-Isopropylmalate Synthesis

By complementation of an alpha-isopropylmalate synthase-negative mutant of Saccharomyces cerevisiae (leu4 leu5), a plasmid was isolated that carried a structural gene for alpha-isopropylmalate synthase. Restriction mapping and subcloning showed that sequences sufficient for complementation of the leu4 leu5 strain were located within a 2.2-kilobase SalI-PvuII segment. Southern transfer hybridization indicated that the cloned DNA was derived intact from the yeast genome. The cloned gene was identified as LEU4 by integrative transformation that caused gene disruption at the LEU4 locus. When this transformation was performed with a LEU4fbr LEU5 strain, the resulting transformants had lost the 5',5',5'-trifluoro-D,L-leucine resistance of the recipient strain but were still Leu+. When it was performed with a LEU4 leu5 recipient, the resulting transformants were Leu-. The alpha-isopropylmalate synthase of a transformant that carried the LEU4 gene on a multicopy plasmid (in a leu5 background) was characterized biochemically. The transformant contained about 20 times as much alpha-isopropylmalate synthase as wild type. The enzyme was sensitive to inhibition by leucine and coenzyme A, was inactivated by antibody generated against alpha-isopropylmalate synthase purified from wild type and was largely confined to the mitochondria. The subunit molecular weight was 65,000-67,000. Limited proteolysis generated two fragments with molecular weights of about 45,000 and 23,000. Northern transfer hybridization showed that the transformant produced large amounts of LEU4-specific RNA with a length of about 2.1 kilonucleotides. The properties of the plasmid-encoded enzyme resemble those of a previously characterized alpha-isopropylmalate synthase that is predominant in wild-type cells. The existence in yeast of a second alpha-isopropylmalate synthase activity that depends on the presence of an intact LEU5 gene is discussed.     

Visual fields of orb web and single line web spiders of the family Uloboridae (Arachnida,Araneida)

Summary In the family Uloboridae, web reduction is associated with changes in web monitoring posture and prosomal features. A spider must extend its first pair of legs directly forward to monitor the signal line of a reduced web. This posture is facilitated by shifts in prosomal musculature that cause reduced web uloborids to have a narrower anterior prosoma, a reduced or absent anterior eye row, and prominent posterior lateral eye tubercles. The eye tubercles and larger posterior eyes of these uloborids suggest that web reduction may also be accompanied by ocular changes that compensate for reduction of the anterior eyes by expanding the visual fields of the posterior eyes. A comparison of the visual fields of the eight-eyed, orb web species Octonoba octonaria and a four-eyed, reduced web Miagrammopes species was made to determine if this is true. Physical and optical measurements determined the visual angles of each species' eyes and the pattern of each species' visual surveillance. Despite loss of the anterior four eyes, the Miagrammopes species has a visual coverage similar to that of O. octonaria. This is due to (1) an increase in the visual field of each of the four remaining Miagrammopes eyes, accruing from an extension of the retina and an increase in the lens' rear radius of curvature, and (2) a ventral shift of each visual axis, associated with the development of an eye tubercle and an asymmetrical expansion of the retina. Miagrammopes monitor their simple webs from twigs or moss where they are vulnerable to predation. Therefore, maintenance of visual cover may enable them to detect predators in time to assume or maintain their characteristic, cryptic posture. It may also allow them to observe approaching prey and permit them to adjust web tension or prepare to jerk their webs when prey strikes.     

Temperature-sensitive vaccinia virus mutants identify a gene with an essential role in viral replication.

Vaccinia virus mutants ts2 and ts25, members of the same complementation group, exhibit a temperature-dependent arrest at the stage of viral DNA replication. The lesions responsible for the mutant phenotypes have been localized to the far left region of the HindIII B genomic fragment by marker rescue studies. Hybrid selection analyses established that the DNA fragments positive for rescue represented the first open reading frame of the HindIII B fragment and encoded a 30-kilodalton protein. The gene is expressed early after infection as a rightwardly transcribed 1-kilobase-pair mRNA whose coordinates were determined by S1 nuclease mapping. To further the phenotypic analysis of the mutants, the accumulation of viral DNA sequences during permissive and nonpermissive infections was quantitated. The extent of the DNA- phenotype was shown to vary in different cell types. In mouse L cells at either high or low multiplicity of infection, nonpermissive DNA synthesis was less than 5% of that seen in permissive infections. This severe defect was mirrored by correspondingly low viral yields. In infections of BSC40 monkey cells, however, the deficiencies in both DNA synthesis and virus production were far less severe. For one mutant (ts2), the temperature sensitivity in BSC40 cells varied inversely with the multiplicity of infection.     

Cellulose and lignin degradation in forest soils: Response to moisture,temperature, and acidity

The concentration of lignin in plant tissue is a major factor controlling organic matter degradation rates in forest ecosystems. Microbial biomass and lignin and cellulose decomposition were measured for six weeks in forest soil microcosms in order to determine the influence of pH, moisture, and temperature on organic matter decomposition. Microbial biomass was determined by chloroform fumigation; lignin and cellulose decomposition were measured radiometrically. The experiment was designed as a Latin square with soils of pH of 4.5, 5.5, and 6.5 adjusted to 20, 40, or 60% moisture content, and incubated at temperatures of 4, 12, or 24°C. Microbial biomass and lignin and cellulose decomposition were not significantly affected by soil acidity. Microbial biomass was greater at higher soil moisture contents. Lignin and cellulose decomposition significantly increased at higher soil temperatures and moisture contents. Soil moisture was more important in affecting microbial biomass than either soil temperature or soil pH.