The Arabidopsis thaliana Kinesin-5 AtKRP125b Is a Processive, Microtubule-Sliding Motor Protein with Putative Plant-Specific Functions

The formation and maintenance of the mitotic spindle during cell division requires several microtubule-interacting motor proteins. Members of the kinesin-5 family play an essential role in the bipolar organization of the spindle. These highly conserved, homotetrameric proteins cross-link anti-parallel microtubules and slide them apart to elongate the spindle during the equal separation of chromosomes. Whereas vertebrate kinesin-5 proteins are well studied, knowledge about the biochemical properties and the function of plant kinesin-5 proteins is still limited. Here, we characterized the properties of AtKRP125b, one of four kinesin-5 proteins in Arabidopsis thaliana. In in vitro motility assays, AtKRP125b displayed the archetypal characteristics of a kinesin-5 protein, a low velocity of about 20 nm·s−1, and a plus end-directed, processive movement. Moreover, AtKRP125b was able to cross-link microtubules and to slide them apart, as required for developing and maintaining the mitotic spindle. In line with such a function, GFP-AtKRP125b fusion proteins were predominantly detected in the nucleus when expressed in Arabidopsis thaliana leaf protoplasts or Nicotiana benthamiana epidermis cells and analyzed by confocal microscopy. However, we also detected GFP signals in the cytoplasm, suggesting additional functions. By generating and analyzing AtKRP125b promoter-reporter lines, we showed that the AtKRP125b promoter was active in the vascular tissue of roots, lateral roots, cotyledons, and true leaves. Remarkably, we could not detect promoter activity in meristematic tissues. Taken together, our biochemical data support a role of AtKRP125b in mitosis, but it may also have additional functions outside the nucleus and during interphase

Investitionsentscheidungen bei mehrfachen Zielsetzungen und künstliche Ameisen

Die Auswahl des attraktivsten Portfolios von Investitionsprojekten zählt zu den kritischen Ma-nagementaufgaben. Angesichts mehrfacher Zielsetzungen und komplexer Projektabhängigkeiten bietet sich dazu ein zweistufiges Vorgehen an, das zunächst effiziente Portfolios identifiziert und den Entscheidungsträger anschließend bei der Suche in diesem Lösungsraum unterstützt. Bei einer großen Zahl an Vorschlägen können die möglichen Projektkombinationen aber nicht mehr in akzeptabler Zeit vollständig enumeriert werden. Adaptierte Meta-Heuristiken bieten hier einen Kompromiß zwischen dem Wunsch nach exakter Bestimmung aller Pareto-optimalen Investitionsprogramme und dem dazu nötigen Rechenaufwand. Dieser Beitrag beschreibt den entsprechenden Einsatz künstlicher Ameisen und diskutiert erste numerische Ergebnisse.Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science