During cytokinesis the cytoplasm of a cell is usually divided to

During cytokinesis the cytoplasm of a cell is usually divided to form two daughter cells. individual plasma membranes. Two microtubule-based cytoskeletal networks, the phragmoplast and the pre-prophase band (PPB), jointly control cytokinesis in plants. The bipolar microtubule array of the phragmoplast regulates cell plate deposition towards a cortical position that is usually templated by the ring-shaped microtubule array of the PPB. In contrast to most animal cells, plants do not use centrosomes as foci of microtubule growth initiation. 925705-73-3 Instead, herb microtubule networks are striking examples of self-organizing systems that emerge from actually constrained interactions of dispersed microtubules. Here we will discuss how microtubule-based activities including growth, shrinkage, severing, sliding, nucleation and bundling interrelate to jointly generate the required ordered AF6 structures. Evidence mounts that adapter proteins sense the local geometry of microtubules to locally modulate the activity of proteins involved in microtubule growth rules and severing. Many of the proteins and mechanisms involved have functions in other microtubule assemblies as well, bestowing broader relevance to insights gained from plants. (Gardner et al. 2013). Changes between the two says are termed and respectively. Dynamic instability is usually most pronounced at the so-called plus-end of microtubules, but also the minus-end can have different says, being primarily static or shrinking (Ehrhardt and Shaw 2006). Throughout the eukaryotic kingdom, the dynamic state of microtubules is usually controlled by a host of conserved proteins (Subramanian and Kapoor 2012). Moreover, lateral associations between microtubules are facilitated by bundling proteins and specialized motor proteins. The latter activity can generate a pressure to slide microtubules along each other (Kapitein et al. 2005; Janson et al. 2007; Peterman and Scholey 2009). Finally, existing microtubules can become severed to form two new microtubules (Roll-Mecak and McNally 2010). To mechanistically understand the formation of 925705-73-3 ordered microtubule networks for herb cell division it will be key to investigate microtubule nucleation, mechanics, bundling, sliding, and severing in an integral manner. Here, we will focus on recent progress on two plant-specific networks, the CA and the phragmoplast and will discuss how feedback between different microtubule activities is usually organized. Division plane selection As already pointed out, the orientation of the division plane is usually decided by the PPB, which in turn inherits its orientation from the CA. The CA consists of microtubules associated to the inner face of the plasma membrane and is usually linked to the cell wall by an as yet unidentified molecular component. It is usually by now well established that microtubules of the CA are able to self-organize into a highly aligned state, whose default orientation is usually transverse to the growth direction of the cell (Ehrhardt and Shaw 2006). The driving pressure for this ordering process are collisions between growing plus-ends and other obstructing microtubules (Dixit and Cyr 2004). In such a collision the incoming growing microtubule can either bend and continue to grow alongside the obstructing microtubulean event called or or . A number of modelling studies have shown that, provided there are enough of these collisions, requiring e.g. a high enough rate of nucleation of new microtubules, spontaneous alignment of microtubules will occur (Allard et al. 2010b; Eren et al. 2010; Tindemans et al. 2010; Hawkins et al. 2010). There is still some debate on which of these collision outcomes is necessary and/or sufficient to explain the ordering process, but it is clear that induced catastrophes by themselves are a sufficient cause (Deinum and Mulder 2013). The relative probabilities of collision outcomes were shown to be dependent on the interaction angle and differ between cell types (Dixit and Cyr 2004; Wightman and Turner 2007). Control over collision outcomes may well involve microtubule bundling proteins and physical forces that are generated during collisions of cortically adhered microtubules (Allard et al. 2010a; Portran et al. 2013). There is also increasing evidence that selective severing of microtubules at cross-over sites by the severing protein katanin, 925705-73-3 in conjunction with adaptor proteins such as SPIRAL2, plays an important role in establishing and maintaining proper organization of the CA (Wightman and Turner 2007; Wightman et al. 2013; Zhang et al. 2013; Lindeboom et al. 2013). The mechanism of relative alignment in itself is not sufficient to explain the lining up of microtubules in a particular direction for division plane selection. Here it turns out there is a key role for cell 925705-73-3 shape, and more specifically for the edges between the different cell faces in coaxing alignment into a particular direction. A notable physical difference between these edges is their radius of curvature. Cell edges that are generated when a new cell wall is constructed during.

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