Properties of broad bean yellow band virus, a possible new tobravirus

A virus was transmitted from broad bean plants in Apulia (Southern Italy) with leaves showing yellow rings, line patterns or yellow vein banding and malformations and necrosis of pods. Symptoms in some, but not all, test plants were similar to those induced by tobraviruses. Purified virus preparations contained two classes of rod-shaped particles containing c. 5% nucleic acid with sedimentation coefficients of 186S and 276S. After centrifugation to equilibrium in CsCl gradients, two components were resolved, with buoyant densities of 1·298 and 1·316 g/cm³. Unfractionated virus preparations contained two species of single-stranded RNA with mol. wts of c. 1·06 × 10⁶ and 2·48 × 10⁶ and one species of coat protein with mol. wt of c. 21 300. The modal lengths of the two classes of particles, both in plant sap and in purified preparations, were 77 nm (S particles) and 202 nm (L particles). L particles accumulated in infected cells in paracrystalline aggregates, whereas S particles were randomly distributed in the cytoplasm of cells. The virus was serologically unrelated to two isolates of tobacco rattle virus and two isolates of pea early-browning virus. The virus, named broad bean yellow band, is considered a distinct tobravirus.     

Carnivorous mammals as seed dispersers of Myrtus communis (Myrtaceae) in the Mediterranean shrublands

ABSTRACT

The role of carnivorous mammals as seed dispersers of Myrtus communis L. in the Mediterranean environment was studied. Seeds of M. communis were found in faeces of red fox (Vulpes vulpes L.) and carnivores from the genus Martes, at four sites on the Tyrrhenic coast of Southern Italy in the period autumn-winter 1993–1995. All the study sites are covered by Mediterranean shrublands with M. communis as one of the dominant species. Content analysis of fox scats showed that fruits of M. communis constitute a relevant component of the diet of these carnivores, although other food categories were also well represented. Further investigations on the effect of mammal digestion on seed germinability showed that carnivores not only moved the seeds away from the mother plant but also enhanced their germinability. This species was known to be bird- and ant-dispersed and the adaptive implications of a multi-vectorial seed dispersal process is discussed.     

Conformational Flexibility of Choline Derivatives

CHOLINERGIC substrates have been found in a gauche conformation (G), skewed about the C_α–C_β bond of the (CH₃)₃N⁺–CH₂–CH₂–O cholinic fragment in a number of crystal structures^1–11. Sulphur and selenium isologues, on the other hand, with the (CH₃)₃N–CH₂–CH₂–(S,Se) group, are normally in the extended trans conformations (T)^10,12,13. In agreement with the assumption that the reduced spectrum of biological activity of many rigid analogues and C_α or C_β substituted derivatives of acetylcholine can be partially ascribed to the reduction in conformational flexibility^14–17, a theoretical investigation¹⁸ predicted the existence of four almost isoenergetic conformations TTTT, TGTT, TTGT and TGGT about the ψ₀, ψ₁, ψ₂ and ψ₃ internal rotation angles schematically represented in Fig. 1.