Reinforced Traditional Management is Needed to Save a Declining Meadow Species. A Demographic Analysis

The changes in agricultural practices during the last century have led to a drastic decrease in the number of traditionally managed hay meadows. Also, traditional management practices are often applied more cursorily in the remaining meadows. In combination with an increase in aerial anthropogenic nitrogen deposition, this has led to a loss of biodiversity. To investigate whether the current management is sufficient for maintaining viable populations of a typical meadow plant, Succisa pratensis, we experimentally reinforced the raking and mowing parts of the traditional management over four years in a two-by-two factorial experiment in three traditionally managed wooded hay meadows on the Baltic island of Gotland, Sweden. We found decreased litter and hay production in two of the three studied meadows as a result of our treatments. Plant sizes and asymptotic population growth rates (??) of S. pratensis increased, particularly in plots receiving the combined raking and mowing treatment. Stochastic long-term population growth rates (?? _s ) increased under the reinforced management: projected population sizes 50?years into the future showed a three-fold increase in raked plots and a 17-fold increase in plots that were both raked and mown. Because we found positive responses even in these seemingly well-managed meadows we conclude that it is essential that management is carried out more thoroughly to ensure viable population sizes. Our conclusion applies to most semi-natural grasslands receiving anthropogenic nitrogen, or where traditional management practices are less rigorously applied. We also suggest using biomass estimation instead of vegetation height as a measure of management strength.     

The Structure of the NTPase That Powers DNA Packaging into Sulfolobus Turreted Icosahedral Virus 2

Biochemical reactions powered by ATP hydrolysis are fundamental for the movement of molecules and cellular structures. One such reaction is the encapsidation of the double-stranded DNA (dsDNA) genome of an icosahedrally symmetric virus into a preformed procapsid with the help of a genome-translocating NTPase. Such NTPases have been characterized in detail from both RNA and tailed DNA viruses. We present four crystal structures and the biochemical activity of a thermophilic NTPase, B204, from the nontailed, membrane-containing, hyperthermoacidophilic archaeal dsDNA virus Sulfolobus turreted icosahedral virus 2. These are the first structures of a genome-packaging NTPase from a nontailed, dsDNA virus with an archaeal host. The four structures highlight the catalytic cycle of B204, pinpointing the molecular movement between substrate-bound (open) and empty (closed) active sites. The protein is shown to bind both single-stranded and double-stranded nucleic acids and to have an optimum activity at 80°C and pH 4.5. The overall fold of B204 places it in the FtsK-HerA superfamily of P-loop ATPases, whose cellular and viral members have been suggested to share a DNA-translocating mechanism.