Pre‐copulation intervals,copulation frequencies,and initial progeny sex ratios in two biotypes of whitefly,Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre‐copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre‐copulation interval and the initial frequency of egg fertilization. Here, we used a video‐recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post‐emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post‐emergence and the majority of females can become fertilized on the day that they emerge.     

Position-dependent sequence elements downstream of AAUAAA are required for efficient rabbit beta-globin mRNA 3' end formation

We previously demonstrated that a critical 35 bp region 3' of the AAUAAA is required for rabbit beta-globin mRNA 3' end formation. Recently, we synthesized and tested sequence elements derived from this region. Here, we report that a GU-rich and a U-rich sequence element are both required for efficient rabbit beta-globin mRNA 3' end formation. The efficiency of processing is restored to the wild-type level when the two elements are placed together and is greatly diminished when only one element is present. The level of 3' end formation is also decreased when the distance between the two elements is expanded. These results demonstrate that the GU-rich and U-rich elements function synergistically to restore efficient mRNA 3' end formation and that they most likely form a single requisite sequence 3' of the AAUAAA. Furthermore, we show that the effect of the GU-rich and U-rich sequence elements is position-dependent.     

Isolation of full-length putative rat lysophospholipase cDNA using improved methods for mRNA isolation and cDNA cloning

We have cloned a full-length putative rat pancreatic lysophospholipase cDNA by an improved mRNA isolation method and cDNA cloning strategy. These new methods allow the construction of a cDNA library from the adult rat pancreas in which the majority of recombinant clones contained complete sequences for the corresponding mRNAs. A previously recognized but unidentified long and relatively rare cDNA clone containing the entire sequence from the cap site at the 5' end to the poly(A) tail at the 3' end of the mRNA was isolated by single-step screening of the library. The size, amino acid composition, and the activity of the protein expressed in heterologous cells strongly suggest this mRNA codes for lysophospholipase [Van den Bosch, H., Aarsman, A. J., DeJong, G. N., & Van Deenen, L. M. (1973) Biochim. Biophys. Acta 296, 94-104].     

Expression of rat transforming growth factor alpha mRNA during development occurs predominantly in the maternal decidua.

Previous studies have shown that transforming growth factor alpha is expressed during rodent development. To establish the site(s) of transforming growth factor alpha mRNA expression during rat embryogensis, we performed in situ hybridization and Northern blot analyses on samples of embryonic and maternal tissues at various gestational ages. Our results indicate that the high levels of transforming growth factor alpha mRNA that are observed during early development are the result of expression in the maternal decidua and not in the embryo. Decidual expression appears to be induced after implantation, peaks at day 8, and then slowly declines through day 15 at which time the decidua is being resorbed. Expression of transforming growth factor alpha mRNA is highest in that region of the decidua adjacent to the embryo and is low or nondetectable in the uterus, placenta, and other maternal tissues. The developmentally regulated expression of transforming growth factor alpha mRNA in the decidua, together with the presence of epidermal growth factor receptors in this tissue, suggests that transforming growth factor alpha stimulates proliferation locally through an autocrine mechanism. Since epidermal growth factor receptors are present in the embryo and placenta, transforming growth factor alpha produced in the decidua may also act on these tissues through paracrine or endocrine mechanisms.     

Separation of chitosomes and secretory vesicles from the “slime” variant of Neurospora crassa

Cells from the slime variant of Neurospora crassa were broken in isotonic conditions by use of triethanolamine buffer plus EDTA. After removal of large membranous structures by low-speed centrifugation, chitosomes and secretory vesicles were separated by means of gel filtration, precipitation of membranous contaminants with Concanavalin A, and centrifugation in sucrose or glycerol gradients. Polypeptidic composition of fractions enriched in secretory vesicles or chitosomes was found to be distinct. By these criteria we concluded that chitosomes and secretory vesicles represent different populations of microvesicles. Both microvesicular populations appeared free of endoplasmic reticulum and vacuolar contaminants as demonstrated by determination of appropriate enzymatic markers.Abbreviations ER Endoplasmic reticulum - UDP-GlcNAc uridine-5-diphosphate N-acetyl glucosamine - GlcNAc N-acetyl glucosamine - SDS sodium dodecyl sulfate - PMSF phenyl methyl sulfonyl fluoride - EDTA ethylene diamino tetraacetic acid Investigador Nacional de Mexico. On leave from the Centro de Investigacion y Estudios Avanzados (IPN), and the Universidad de Guanajuato, Gto., Mexico     

Relationship of alcohol production to lipid composition of yeast in a continuous flow bioreactor

Saccharomyces cerevisiae was cultivated in a controlled aerated, dual-stage (column), continuous flow bioreactor in a hybrid free-cell and immobilized-cell state. The yeast cells maintained an ethanol concentration of 58-64 and 91-98 g/L in stages I and II, respectively. The lipid composition of the cells cultivated under these conditions was correlated to the effects of aeration by interrupting the aeration on days 113 and 266 of continuous operation. Under conditions of aeration or nonaeration, an alternating increase and decrease in the contents of squalene, sterols, and fatty acids of the respiratory-competent and -deficient unattached free cells was observed. The cellular free lipid compositions of the immobilized cells in the aerated and nonaerated conditions were similar and characteristic of respiratory-deficient cells with the exception of the immobilized cells exposed to a higher ethanol concentration (stage II). These cells contained a broader range of sterol components and increased levels of unsaturated fatty acids than immobilized cells at a lower ethanol concentration (stage I). The neutral lipid to phospholipid ratio decreased for respiratory-deficient cells with phosphatidylethanolamine and phosphatidylinositol being the principal phospholipids. The data demonstrated the essentiality of the hybrid bioreactor design for continuous long term performance and the importance of maintaining specific yeast lipid constituents for continuous high alcohol productivity.