IntroductionInactivation of proteins that participate in more than one cellular process leads to a variety of apparently unconnected phenotypes. Understanding the molecular cause for each phenotype might reveal how seemingly independent cellular processes are regulated and coordinated in the cell. Genome-wide gene interaction data based on the simultaneous inactivation of more than one gene greatly facilitate this inherently complex analysis because genes with pleiotropic phenotypes often occupy central positions in the corresponding interaction networks (Costanzo et al., 2010;Tong et al., 2004). By assigning physical connections, protein-protein interaction maps provide the necessary complementary information. Interpretation of these maps is usually not straightforward. Genetic interactions can result from complex functional relationships between the investigated pairs of genes and protein interaction maps are generally projections of contacts that occur at different times and places in the cell. To transform protein interaction data into mechanistically meaningful models, it is necessary to resolve these projections into their different interaction planes. We define an interaction plane or state as the sum of all simultaneously occurring contacts. Ideally, these states should be defined by time-and space-resolved in vivo studies. However, these studies are technically demanding and usually not suited for measuring multiple contacts (Maeder et al., 2007). Using the protein pair Ptc1p-Nbp2p of the yeast Saccharomyces cerevisiae as an example and the split-ubiquitin method (SplitUb) as the experimental tool, we present an alternative approach for defining interaction states. The derived constraint interaction network reduces the number of possible states and thus provides a useful framework for model building and the initiation of more detailed studies.

Eukaryotic cells can direct secretion to defined regions of their plasma membrane. These regions are distinguished by an elaborate architecture of proteins and lipids that are specialized to capture and fuse post-Golgi vesicles. Here, we show that the proteins Boi1p and Boi2p are important elements of this area of active exocytosis at the tip of growing yeast cells. Cells lacking Boi1p and Boi2p accumulate secretory vesicles in their buds. The essential PH domains of Boi1p and Boi2p interact with Sec1p, a protein required for SNARE complex formation and vesicle fusion. Sec1p loses its tip localization in cells depleted of Boi1p and Boi2p but overexpression of Sec1p can partially compensate for their loss. The capacity to simultaneously bind phospholipids, Sec1p, multiple subunits of the exocyst, Cdc42p and the module for generating active Cdc42p identify Boi1p and Boi2p as essential mediators between exocytosis and polar growth.

Due to the local enrichment of factors that influence its dynamics, and organization, the actin cytoskeleton displays different shapes and functions within the same cell. In yeast cells post-Golgi vesicles ride on long actin cables to the bud tip. The proteins Boi1 and Boi2 participate in tethering and docking these vesicles to the plasma membrane. Here we show that Boi1/2 also recruit nucleation and elongation factors to form actin filaments at sites of exocytosis. Disrupting the connection between Boi1/2 and the nucleation factor Bud6 impairs filament formation, reduces the directed movement of the vesicles to the tip, and shortens their tethering time at the cortex. Transplanting Boi1 from the bud tip to the peroxisomal membrane partially redirects the actin cytoskeleton and the vesicular flow towards the peroxisome, and creates an alternative, rudimentary vesicle-docking zone. We conclude that Boi1/2 through their interactions with Bud6 and Bni1 induce the formation of a cortical actin structure that receives and aligns incoming vesicles before fusion with the membrane.

Actomyosin ring (AMR) contraction and the synthesis of an extracellular septum are interdependent pathways that mediate cytokinesis in the yeast Saccharomyces cerevisiae and other eukaryotes. How these interdependent pathways are physically connected is central for understanding cytokinesis. The yeast IQGAP (Iqg1p) belongs to the conserved AMR. The F-BAR-domaincontaining protein Hof1p is a member of a complex that stimulates cell wall synthesis. We report here on the stepwise formation of a physical connection between both proteins. The C-terminal IQrepeats of Iqg1p first bind to the essential myosin light chain before both proteins assemble with Hof1p into the Mlc1p-Iqg1p-Hof1p (MIH) bridge. Mutations in Iqg1p that disrupt the MIH complex alter Hof1p targeting to the AMR and impair AMR contraction. Epistasis analyses of two IQG1 alleles that are incompatible with formation of the MIH complex support the existence and functional significance of a large cytokinetic core complex. We propose that the MIH complex acts as hinge between the AMR and the proteins involved in cell wall synthesis and membrane attachment.

In this study, a new, to the best of our knowledge, form of odd-Pearcey Gauss beams with peculiar characteristics is presented. Compared with the Pearcey beam, the odd-Pearcey Gauss beam is symmetrical about the origin. At the initial stages, the odd-Pearcey Gauss beam propagates with a main central lobe and some residual spots that autofocus to the center, and then splits into two off-axis parabolic lobes after the autofocus finishes. Furthermore, we also introduce the soft well function to investigate the propagation profiles of the odd-Pearcey Gauss beams passing through it with different calibers and discuss the influence of the Gaussian waist width towards the focal distance and the propagation form of the odd-Pearcey Gauss beam. We also enumerate some potential and possible applications based on its peculiar characteristics.