TY - JOUR AB - A cell membrane can be considered a liquid-phase plane in which lipids and proteins theoretically are free to diffuse. Numerous reports,however, describe retarded diffusion ofmembrane proteins in animal cells. This anomalous diffusion results from a combination of structuring factors including protein-protein interactions, cytoskeleton corralling, and lipid organization into microdomains. In plant cells, plasma-membrane (PM) proteins have been described as relatively immobile, but the control mechanisms that structure the PM have not been studied. Here, we use fluorescence recovery after photobleaching to estimate mobility of a set of minimal PM proteins. These proteins consist only of a PM-anchoring domain fused to a fluorescent protein, but their mobilities remained limited, as is the case for many full-length proteins. Neither the cytoskeleton nor membrane microdomain structure was involved in constraining the diffusion of these proteins. The cell wall, however, was shown to have a crucial role in immobilizing PM proteins. In addition, by single-molecule fluorescence imaging we confirmed that the pattern of cellulose deposition in the cell wall affects the trajectory and speed ofPMprotein diffusion. Regulation ofPMprotein dynamics by the plant cell wall can be interpreted as a mechanism for regulating protein interactions in processes such as trafficking and signal transduction. AU - Martinière, Alexandre AU - Lavagi, Irene AU - Nageswaran, Gayathri AU - Rolfe, Daniel J AU - Maneta-Peyret, Lilly AU - Luu, Doan-Trung AU - Botchway, Stanley W AU - Webb, Stephen E AU - Mongrand, Sebastien AU - Maurel, Christophe AU - Martin-Fernandez, Marisa L AU - Kleine-Vehn, Jürgen AU - Jirí Friml AU - Moreau, Patrick AU - Runions, John ID - 3113 IS - 31 JF - PNAS TI - Cell wall constrains lateral diffusion of plant plasma membrane proteins VL - 109 ER - TY - JOUR AB - Auxin is a key coordinative signal required for many aspects of plant development and its levels are controlled by auxin metabolism and intercellular auxin transport. Here we find that a member of PIN auxin transporter family, PIN8 is expressed in male gametophyte of Arabidopsis thaliana and has a crucial role in pollen development and functionality. Ectopic expression in sporophytic tissues establishes a role of PIN8 in regulating auxin homoeostasis and metabolism. PIN8 co-localizes with PIN5 to the endoplasmic reticulum (ER) where it acts as an auxin transporter. Genetic analyses reveal an antagonistic action of PIN5 and PIN8 in the regulation of intracellular auxin homoeostasis and gametophyte as well as sporophyte development. Our results reveal a role of the auxin transport in male gametophyte development in which the distinct actions of ER-localized PIN transporters regulate cellular auxin homoeostasis and maintain the auxin levels optimal for pollen development and pollen tube growth. AU - Ding, Zhaojun AU - Wang, Bangjun AU - Moreno, Ignacio AU - Dupláková, Nikoleta AU - Sibu Simon AU - Carraro, Nicola AU - Reemmer, Jesica AU - Pěnčík, Aleš AU - Xu Chen AU - Tejos, Ricardo I AU - Skůpa, Petr AU - Pollmann, Stephan AU - Mravec, Jozef AU - Petrášek, Jan AU - Zažímalová, Eva AU - Honys, David AU - Rolčík, Jakub AU - Murphy, Angus S AU - Orellana, Ariel AU - Geisler, Markus AU - Jirí Friml ID - 3114 IS - AN 941 JF - Nature Communications TI - ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis VL - 3 ER - TY - JOUR AB - PIN-FORMED (PIN) protein-mediated auxin polar transport is critically important for development, pattern formation, and morphogenesis in plants. Auxin has been implicated in the regulation of polar auxin transport by inhibiting PIN endocytosis [1, 2], but how auxin regulates this process is poorly understood. Our genetic screen identified the Arabidopsis SPIKE1 (SPK1) gene whose loss-of-function mutations increased lateral root density and retarded gravitropic responses, as do pin2 knockout mutations [3]. SPK1 belongs to the conserved DHR2-Dock family of Rho guanine nucleotide exchange factors [4-6]. The spk1 mutations induced PIN2 internalization that was not suppressed by auxin, as did the loss-of-function mutations for Rho-like GTPase from Plants 6 (ROP6)-GTPase or its effector RIC1. Furthermore, SPK1 was required for auxin induction of ROP6 activation. Our results have established a Rho GTPase-based auxin signaling pathway that maintains PIN2 polar distribution to the plasma membrane via inhibition of its internalization in Arabidopsis roots. Our findings provide new insights into signaling mechanisms that underlie the regulation of the dynamic trafficking of PINs required for long-distance auxin transport and that link auxin signaling to PIN-mediated pattern formation and morphogenesis. AU - Lin, Deshu AU - Nagawa, Shingo AU - Chen, Jisheng AU - Cao, Lingyan AU - Xu Chen AU - Xu, Tongda AU - Hongjiang Li AU - Dhonukshe, Pankaj AU - Yamamuro, Chizuko AU - Jirí Friml AU - Scheres, Ben AU - Fu, Ying AU - Yang, Zhenbiao ID - 3111 IS - 14 JF - Current Biology TI - A ROP GTPase dependent auxin signaling pathway regulates the subcellular distribution of PIN2 in Arabidopsis roots VL - 22 ER - TY - JOUR AB - The dynamic spatial and temporal distribution of the crucial plant signaling molecule auxin is achieved by feedback coordination of auxin signaling and intercellular auxin transport pathways [1, 2]. Developmental roles of auxin have been attributed predominantly to its effect on transcription; however, an alternative pathway involving AUXIN BINDING PROTEIN1 (ABP1) has been proposed to regulate clathrin-mediated endocytosis in roots and Rho-like GTPase (ROP)-dependent pavement cell interdigitation in leaves [3, 4]. In this study, we show that ROP6 and its downstream effector RIC1 regulate clathrin association with the plasma membrane for clathrin-mediated endocytosis, as well as for its feedback regulation by auxin. Genetic analysis revealed that ROP6/RIC1 acts downstream of ABP1 to regulate endocytosis. This signaling circuit is also involved in the feedback regulation of PIN-FORMED 1 (PIN1) and PIN2 auxin transporters activity (via its constitutive endocytosis) and corresponding auxin transport-mediated processes, including root gravitropism and leave vascular tissue patterning. Our findings suggest that the signaling module auxin-ABP1-ROP6/RIC1-clathrin-PIN1/PIN2 is a shared component of the feedback regulation of auxin transport during both root and aerial development. AU - Xu Chen AU - Naramoto, Satoshi AU - Robert, Stéphanie AU - Tejos, Ricardo AU - Löfke, Christian AU - Lin, Deshu AU - Yang, Zhenbiao AU - Jirí Friml ID - 3112 IS - 14 JF - Current Biology TI - ABP1 and ROP6 GTPase signaling regulate clathrin mediated endocytosis in Arabidopsis roots VL - 22 ER - TY - JOUR AB - We consider two-player zero-sum stochastic games on graphs with ω-regular winning conditions specified as parity objectives. These games have applications in the design and control of reactive systems. We survey the complexity results for the problem of deciding the winner in such games, and in classes of interest obtained as special cases, based on the information and the power of randomization available to the players, on the class of objectives and on the winning mode. On the basis of information, these games can be classified as follows: (a) partial-observation (both players have partial view of the game); (b) one-sided partial-observation (one player has partial-observation and the other player has complete-observation); and (c) complete-observation (both players have complete view of the game). The one-sided partial-observation games have two important subclasses: the one-player games, known as partial-observation Markov decision processes (POMDPs), and the blind one-player games, known as probabilistic automata. On the basis of randomization, (a) the players may not be allowed to use randomization (pure strategies), or (b) they may choose a probability distribution over actions but the actual random choice is external and not visible to the player (actions invisible), or (c) they may use full randomization. Finally, various classes of games are obtained by restricting the parity objective to a reachability, safety, Büchi, or coBüchi condition. We also consider several winning modes, such as sure-winning (i.e., all outcomes of a strategy have to satisfy the winning condition), almost-sure winning (i.e., winning with probability 1), limit-sure winning (i.e., winning with probability arbitrarily close to 1), and value-threshold winning (i.e., winning with probability at least ν, where ν is a given rational). AU - Chatterjee, Krishnendu AU - Doyen, Laurent AU - Henzinger, Thomas A ID - 3128 IS - 2 JF - Formal Methods in System Design TI - A survey of partial-observation stochastic parity games VL - 43 ER -