Codon Usage Bias and tRNA Abundance in Drosophila

Codon usage bias of 1,117 Drosophila melanogaster genes, as well as fewer D. pseudoobscura and D. virilis genes, was examined from the perspective of relative abundance of isoaccepting tRNAs and their changes during development. We found that each amino acid contributes about equally and highly significantly to overall codon usage bias, with the exception of Asp which had very low contribution to overall bias. Asp was also the only amino acid that did not show a clear preference for one of its synonymous codons. Synonymous codon usage in Drosophila was consistent with ``optimal' codons deduced from the isoaccepting tRNA availability. Interestingly, amino acids whose major isoaccepting tRNAs change during development did not show as strong bias as those with developmentally unchanged tRNA pools. Asp is the only amino acid for which the major isoaccepting tRNAs change between larval and adult stages. We conclude that synonymous codon usage in Drosophila is well explained by tRNA availability and is probably influenced by developmental changes in relative abundance. Received: 5 December 1996 / Accepted: 14 June 1997     

Cutting edge: macrophage migration inhibitory factor is necessary for progression of experimental autoimmune encephalomyelitis

Macrophage migration inhibitory factor (MIF) has been implicated in the pathogenesis of inflammatory and autoimmune diseases. The role of MIF in the progression of experimental autoimmune encephalomyelitis (EAE) was explored using MIF-/- mice. Wild-type mice showed a progressive disease course, whereas MIF-/- mice exhibited acute signs but no further progression of clinical disease. MIF-/- mice displayed markedly elevated corticosterone levels and significant decreases in the inflammatory cytokines TNF-alpha, IFN-gamma, IL-2, and IL-6 before, during, and after EAE onset. Taken together, these findings support that MIF is an important mediator of EAE progression through glucocorticoid antagonism and up-regulation of the inflammatory response.     

Female sterility in hybrids between Anopheles gambiae and A. arabiensis, and the causes of Haldane's rule

Although F1 female hybrids between Anopheles gambiae and A. arabiensis are fully fertile, sterility is present in backcross females. Here we report the results of a study into the genetic basis of backcross female sterility. Using 23 markers, we performed quantitative trait loci (QTL) mapping analyses to identify chromosomal regions involved in hybrid female sterility. We found that female sterility in backcrosses in both directions is primarily caused by interspecific interactions between a heterozygous X chromosome and recessive autosomal factors. In addition, our data provide support for two theories implicated in Haldane's rule in a single taxon. A comparison with data from a previous study shows that male hybrid sterility QTL are present in higher numbers than female hybrid sterility QTL. Furthermore, autosomal female sterility factors tend to be recessive, supporting the dominance theory for female sterility. Finally, our data indicate a very large effect of the X chromosome from both species on hybrid female sterility, despite the fact that the X chromosome represents less than 9% of the genome. However, this could be the result of a lack of introgression of the X chromosome between A. gambiae and A. arabiensis, rather than a faster evolution of sterility factors on the X chromosome.     

Water-soluble proteins of mature barley endosperm: genetic control,polymorphism, and linkage with β-amylase and spring/winter habit

Summary Water-soluble proteins (WSP-2 and WSP-3) and -amylase (-AMY-1) were extracted from mature endosperms of 44 spring and 39 winter barley genotypes. The protein and enzyme isoforms were separated in isoelectric focusing gels with a pH gradient of 4–6.5. The Wsp-3 and -Amy-1 loci were located to chromosomes 4H using the wheat/barley chromosome addition lines. Segregation analysis of F₂ and doubled haploid populations showed Wsp-2 and -Amy-1 to be tightly linked, with a map distance of 11 cMorgans. Isoforms of WSP-2 possessed similar pIs to that of WSP-3 and overlapping bands were observed in the gels. These bands segregated independently in F₂ and doubled haploid populations, implying two unlinked genes. All three loci were found to be polymorphic: two alleles were detected at the Wsp-2 locus, three at Wsp-3 and two at -Amy-1. The frequency of alleles at all three loci was found to be different in winter and spring genotypes. Spring genotypes possessed a wider range of phenotypes than winter genotypes. Spring and winter genotypes could be distinguished on the basis of WSP-3 and - AMY-1 phenotypes. The linkage between Wsp-3 and -Amy-1 loci and genes controlling spring/winter habit on chromosome 4H is discussed. It is concluded that Wsp-3 and -Amy-1 can be used as genetic markers for spring/winter habit in barley genetic research and breeding.     

Control of flowering time in temperate cereals: genes, domestication, and sustainable productivity

The control of flowering is central to reproductive success in plants, and has a major impact on grain yield in crop species. The global importance of temperate cereal crops such as wheat and barley has meant emphasis has long been placed on understanding the genetics of flowering in order to enhance yield. Leads gained from the dissection of the molecular genetics of model species have combined with comparative genetic approaches, recently resulting in the isolation of the first flowering time genes in wheat and barley. This paper reviews the genetics and genes involved in cereal flowering pathways and the current understanding of how two of the principal genes, Vrn and Ppd, have been involved in domestication and adaptation to local environments, and the implications for future breeding programmes are discussed.     

Tightly bound zinc in human immunodeficiency virus type 1, human T-cell leukemia virus type I, and other retroviruses.

Human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus type I (HTLV-I) were purified by sucrose density gradient centrifugation in the presence of 1 mM EDTA. Pelleted gradient fractions were analyzed for total protein, total Gag capsid protein, and total zinc. Zinc was found to copurify and concentrate with the virus particles. Through successive cycles of resuspending in buffer containing EDTA and repelleting, the zinc content remained constant at about 1.7 mol of zinc per mol of Gag protein. Proteins from purified virus (HIV-1 and HTLV-I) were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, blotted to polyvinylidene fluoride paper, and probed with 65ZnCl2. Viral nucleocapsid (NC) proteins (HIV-1 p7NC and HTLV-I p15NC) bound 65Zn2+. Other retroviruses, including simian immunodeficiency virus, equine infectious anemia virus, bovine leukemia virus, Moloney murine leukemia virus, mouse mammary tumor virus, and Mason-Pfizer monkey virus, were found to contain amounts of zinc per milligram of total protein similar to those found in HIV-1 and HTLV-I. Collectively, these data support the hypothesis that retroviral NC proteins function as zinc finger proteins in mature viruses.     

Microsatellite analysis of relationships within cultivated potato (Solanum tuberosum)

The potential of microsatellite markers for use in genetical studies in potato (Solanum tuberosum) was evaluated. Database searches revealed that microsatellite sequences were present in the non-coding regions of 24 potato genes. Twenty-two sets of primers were designed and products successfully amplified using 19 primer pairs. These were tested against a panel of 18 tetraploid potato cultivars. Four pairs of primers designed to amplify microsatellites from tomato were also used. Seven (including 2 of the tomato sequences) failed to reveal any variation in the accessions tested. Sixteen primer pairs did reveal polymorphism, detecting between 2 and 19 alleles at each locus. Of these, 3 gave rise to complex band patterns, suggesting that multiple polymorphic loci were being amplified using a single primer pair. Heterozygosity values ranged from 0.408 to 0.921. Phenetic analysis of the derived information allowed a dendrogram to be constructed depicting the relationships between the 18 potato cultivars. The potential of microsatellite markers for genetic analysis and satutory applications in potato is discussed in the context of these results. Furthermore, the potential of crossspecies amplification is highlighted as an additional source of microsatellite markers for genetic research in potato.     

Transgenic expression of pear PGIP in tomato limits fungal colonization

Transgenic tomato plants expressing the pear fruit polygalacturonase inhibitor protein (pPGIP) were used to demonstrate that this inhibitor of fungal pathogen endopolygalacturonases (endo-PGs) influences disease development. Transgenic expression of pPGIP resulted in abundant accumulation of the heterologous protein in all tissues and did not alter the expression of an endogenous tomato fruit PGIP (tPGIP). The pPGIP protein was detected, as expected, in the cell wall protein fraction in all transgenic tissues. Despite differential glycosylation in vegetative and fruit tissues, the expressed pPGIP was active in both tissues as an inhibitor of endo-PGs from Botrytis cinerea. The growth of B. cinerea on ripe tomato fruit expressing pPGIP was reduced, and tissue breakdown was diminished by as much as 15%, compared with nontransgenic fruit In transgenic leaves, the expression of pPGIP reduced lesions of macerated tissue approximately 25%, a reduction of symptoms of fungal growth similar to that observed with a B. cinerea strain in which a single endo-PG gene, Bcpg1, had been deleted (A. ten Have, W. Mulder, J. Visser, and J. A. L. van Kan, Mol. Plant-Microbe Interact. 11:1009-1016, 1998). Heterologous expression of pPGIP has demonstrated that PGIP inhibition of fungal PGs slows the expansion of disease lesions and the associated tissue maceration.     

Comparative flight behavior of parasitoids Campoletis sonorensis and Microplitis croceipes

Flight behavior of parasitoids Microsplitis croceipes Cresson (Braconidae) and Campoletis sonorensis (Cameron) (Ichneumonidae) was examined in a wind tunnel. Both species exhibited odor directed, oriented flights to cotton, although flight frequency was related to variation in wind velocity or differential cotton volatile emission with changes in wind velocity, or both. Flight frequency at constant wind velocity was affected by illumination. Microplitis croceipes was attracted to the wind borne odor of Heliothis virescens (F.) frass and larvae, whereas C. sonorensis was not. Possible interaction of the wind borne odors from the habitat and host is suggested for parasitoids.

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Résumé Le comportement de vol de M. croceipes Cres. (Hym. Braconidae) et de C. sonorensis Cam. (Hym. Icheumonidae) a été étudié en olfactométrie dans un tunnel à vent. Les femelles des deux espèces, et non les mâles, ont un vol orienté par l'odeur des feuilles fraîches de coton (Gossypium hirsutum L.). La fréquence d'envol est liée aux changements de vitesse du vent, aux variations d'émissions, par le cotonnier, des substances volatiles, en fonction de la vitesse du vent, ou aux deux. La fréquence d'envol à vitesse de vent constante dépend de l'éclairage. La fréquence d'envol de C. sonorensis augmente avec des intensités lumineuses relativement fortes et diminue avec des intensités relativement faibles. L'inverse est observé avec M. croceipes. Le vent chargé d'odeurs de larves ou d'extréments d'Heliothis virescens F., attire M. croceipes et non C. sonorensis. Nous suggérons une éventuelle interaction des odeurs portées par le vent et provenant de l'habitat et de l'hôte.