Classical potential energy calculations for ApA, CpC, GpG, and UpU. The influence of the bases on RNA subunit conformations

Classical potential energy calculations have been made for the ribodinucleoside monophosphates ApA, CpC, GpG, and UpU. Van der Waal's, electrostatic, and torsional contributions to the energy were calculated, and the energy was minimized with the seven backbone conformational angles as simultaneously variable parameters. At the global minimum, ApA and CpC have conformations like double helical RNA: the angles ω′ and ω are g−g−, the sugar pucker is C3′-endo, and the bases are anti. GpG and UpU, on the other hand, have the ω′,ω angle pair g−t at the global minimum, and for GpG the bases are syn. Energy contour maps for ω′ and ω show two broad, low energy regions for ApA, CpC, and UpU: one is g−g−, and the second encompasses g−t and g+g+ within a single low energy contour. The two regions are connected by a path at 10–13 kcal./mole. For GpG, with bases syn, however, only a small low-energy region at g−t is found. The helical ‘A’ RNA conformation is 8.5 kcal/mole higher for this molecule. Thus, the base composition is shown to influence the conformations adopted by dinucleoside phosphates. Comparison of calculations with experimental data, where available, show good agreement

Towards molecular breeding of barley: Construction of a molecular genetic map

Genetic map construction is an important step towards identifying genes that are responsible for the expression of traits. To achieve this goal a dihaploid mapping population was constructed between the barley parents Tallon and Kaputar. Parents were first screened with amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers. A total of 211 AFLP markers and 33 SSR markers were identified as polymorphic between the parents. Then all of the polymorphic AFLP markers and 24 of the SSR markers were assayed for the whole population. Linkage analysis of the markers revealed seven large and thirteen smaller linkage groups. The seven large linkage groups are assigned to individual barley chromosomes with reference to the published map locations of the SSR markers. The total map covered 1300 cM, which is about the expected size of the barley genome

Ocorrência de vírus esférico causando faixa amarela das nervuras da couve em São Paulo Occurrence of yellow vein banding of cole induced by a spherical virus

Partículas esferoidais de 50-60m&#956; de diâmetro foram encontradas em preparações semipurificadas e em preparações rápidas de plantas de couve infetadas com um vírus que induz faixa amarela das nervuras (VFANC). Essas partículas têm um capsídeo aparentemente icosaedral, constituído de 92 capsômeros de 50-60 A de diâmetro. Quando tratadas com acetato de uranila, revelaram a existência de uma zona central, que se impregna fortemente com êste corante, possìvelmente constituída de nucleoproteína. Tais partículas não foram encontradas em plantas sadias, mas foram nelas detectadas, após serem inoculadas por união de tecidos, por meios mecânicos ou por afídeos com VFANC. Partículas similares foram encontradas em secções ultra-finas de tecido foliar de couve infetado com o VFANC, porém apresentavam um diâmetro ligeiramente menor, da ordem de 35-45m&#956;. Invariàvelmente, essas partículas foram encontradas em meio às inclusões citoplasmáticas de forma e dimensões variadas, constituídas de uma massa amorfa, granular e densa. Tais inclusões puderam também ser observadas em secções mais espêssas e montadas para microscopia óptica. Possìvelmente o VFANC pertence ao grupo do vírus do mosaico da couve-flôr, dada a semelhança na morfologia das partículas e nas moléstias induzidas.<br>Spherical particles, 50-60 m&#956;, in diameter were found in partially purified preparalions, and also in quick preparations made from plants infected with a virus inducing yellow vein banding in cole (Brassica oleracea var. acephala) . These particles apparently had an icosahedral capsid composed by 92 capsomeres, each with 50-60 A in diameter. Uranyl acetate treatment of these particles revealed a central zone, about 25-30 m&#956; in diameter, which bound strongly with the stain, indicating that this part of the particle is nucleoprotein. Such particles were absent in healthy plants, but they were detected after these plants were inoculated by tissue union, mechanically, or by aphids with the cole yellow vein banding virus. Similar particles were found in ultrathin leaf sections from cole infected by yellow vein banding virus, invariably embedded in a cytoplasmic inclusion body, but their diameters were slightly smaller (35-45 m&#956;). These inclusions, with variable dimensions and shape, were composed by an amorphous, dense and granular matrix, and were detectable even under light microscope level in thicker sections. It is likely that the above described virus is related to the cauliflower mosaic virus, due to the similarities in particle morphology and induced diseases