Mathematical model of plant-virus interactions mediated by RNA interference

Cross-protection, which refers to a process whereby artificially inoculating a plant with a mild strain provides protection against a more aggressive isolate of the virus, is known to be an effective tool of disease control in plants. In this paper we derive and analyse a new mathematical model of the interactions between two competing viruses with particular account for RNA interference. Our results show that co-infection of the host can either increase or decrease the potency of individual infections depending on the levels of cross-protection or cross-enhancement between different viruses. Analytical and numerical bifurcation analyses are employed to investigate the stability of all steady states of the model in order to identify parameter regions where the system exhibits synergistic or antagonistic behaviour between viral strains, as well as different types of host recovery. We show that not only viral attributes but also the propagating component of RNA-interference in plants can play an important role in determining the dynamics

NORDITERPENOID ALKALOIDS OF DELPHINIUM-MUNZIANUM

Five new norditerpenoid alkaloids, 14-O-benzoylperegrine, 14-O-acetylperegrine, munzinanone, munzianine and 10-hydroxyperegrine, together with peregrine and 14-O-methylperegrine, were isolated from Delphinium munzianum. The structures of the new alkaloids were elucidated mainly by NMR spectroscopy, including 2-D techniques, and partial synthesis starting from peregrine