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An Arabidopsis Lipid Flippase Is Required for Timely Recruitment of Defenses to the Host- Pathogen Interface at the Plant Cell Surface

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Molecular Plant 2017年第6期10卷 805-820页

作者： William Underwood Andrew Ryan Shauna C. Somerville Energy Biosciences Institute Department of Plant and Microbial Biology University of California Berkeley CA 94720 USA USDA-ARS Red River Valley Agricultural Research Center Sunflower and Plant Biology Research Unit Fargo ND 58102-2765 USA Division of Biological Sciences University of California San Diego CA 92161 USA

Deposition of cell wall-reinforcing papillae is an integral component of the plant immune response. TheArabidopsis PENETRATION 3 （PEN3） ATP binding cassette （ABC） transporter plays a role in defense against numerous pathogens and is recruited to sites of pathogen detection where it accumulates within papillae. However, the trafficking pathways and regulatory mechanisms contributing to recruitment of PEN3 and other defenses to the host-pathogen interface are poorly understood. Here, we report a confocal microscopy-based screen to identify mutants with altered localization of PEN3-GFP after inoculation with powdery mildew fungi. We identified a mutant, aberrant localization of PEN3 3 （alp3）, displaying accumulation of the normally plasma membrane （PM）-Iocalized PEN3-GFP in endomembrane compartments. The mutant was found to be disrupted in the P4-ATPase AMINOPHOSPHOLIPID ATPASE 3 （ALA3）, a lipid flippase that plays a critical role in vesicle formation. We provide evidence that PEN3 undergoes continuous endocytic cycling from the PM to the trans-Golgi network （TGN）. In alp3, PEN3 accumulates in the TGN, causing delays in recruitment to the host-pathogen interface. Our results indicate that PEN3 and other defense proteins continuously cycle through the TGN and that timely exit of these proteins from the TGN is critical for effective pre-invasive immune responses against powdery mildews.

关键词： plant-microbe interactions defense responses protein traffic and secretion macromolecular trafficking papilla ABC transporter

Inositol Polyphosphate Phosphatidylinositol 5-Phosphatase9 （At5PTase9） Controls Plant Salt Tolerance by Regulating Endocytosis

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Molecular Plant 2013年第6期6卷 1781-1794页

作者： Yael Golania Yuval Kaye Omri Gilhar Mustafa Ercetin Glenda Gillaspy Alex Levine Department of Plant and Environmental Sciences The Hebrew University of Jerusalem Givat-Ram Campus Jerusalem 91904 Israel Department of Biochemistry and Fralin Biotechn01ogy Center Virginia T'ech Blacksburg VA 24061 USA

Phosphatidylinositol 5-phosphatases （5PTases） components of membrane trafficking system. Recently, we that hydrolyze the 5＇ position of the inositol ring are key reported that mutation in AtSPTase7 gene reduced produc- tion of reactive oxygen species （ROS） and decreased expression of stress-responsive genes, resulting in increased salt sensitivity. Here, we describe an even more salt-sensitive 5ptase mutant, At5ptase9, which also hydrolyzes the 5＇ phos- phate groups specifically from membrane-bound phosphatidylinositides. Interestingly, the mutants were more tolerant to osmotic stress. We analyzed the main cellular processes that may be affected by the mutation, such as production of ROS, influx of calcium, and induction of salt-response genes. The At5ptase9 mutants showed reduced ROS produc- tion and Ca2~ influx, as well as decreased fluid-phase endocytosis. Inhibition of endocytosis by phenylarsine oxide or Tyrphostin A23 in wild-type plants blocked these responses. Induction of salt-responsive genes in wild-type plants was also suppressed by the endocytosis inhibitors. Thus, inhibition of endocytosis in wild-type plants mimicked the salt stress responses, observed in the AtSptase9 mutants. In summary, our results show a key non-redundant role of At5PTase7 and 9 isozymes, and underscore the localization of membrane-bound Ptdlns in regulating plant salt tolerance by coordinating the endocytosis, ROS production, Ca2＋ influx, and induction of stress-responsive genes.

关键词： abiotic/environmental stress oxidative and photo-oxidative stress salinity protein traffic and secretion gene expression Arabidopsis.

Cell Polarity Signaling： Focus on Polar Auxin Transport

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Molecular Plant 2008年第6期1卷 899-909页

作者： Xiaowei Gao Shingo Nagawa Genxuan Wang Zhenbiao Yang Key Laboratory of Arid and Grassland Agroeology at Lanzhou University Ministry of Education Lanzhou 730000 China CAU-UCR Joint Center for Biological Science China Agricultural University Beijing 100094 China Center for Plant Cell Biology and Department of Botany and Plant Science University of California Riverside CA 92521 USA College of Life Science Zhejiang University Hangzhou 310029 China

Polar auxin transport, which is required for the formation of auxin gradients and directional auxin flows that are critical for plant pattern formation, morphogenesis, and directional growth response to vectorial cues, is mediated by polarized sub-cellular distribution of PIN-FORMED proteins （PINs, auxin efflux carriers）, AUX1/AUXI-like proteins （auxin influx facilitators）, and multidrug resistance P-glycoproteins （MDR/PGP）. Polar localization of these proteins is controlled by both developmental and environmental cues. Recent studies have revealed cellular （endocytosis, transcytosis, and endosomal sorting and recycling） and molecular （PINOID kinase, protein phosphatase 2A） mechanisms underlying the polar distribution of these auxin transport proteins. Both TIR1-mediated auxin signaling and TIRl-independent auxinmediated endocytosis have been shown to regulate polar PIN localization and auxin flow, implicating auxin as a selforganizing signal in directing polar transport and directional flows.

关键词： PIN proteins PINOID ROP GTPases polarity protein traffic and secretion signal transduction.

Transport Logistics in Pollen Tubes

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Molecular Plant 2013年第4期6卷 1037-1052页

作者： Youssef Chebli Jens Kroeger Anja Geitmann Departement de sciences biologiques Institut de recherche en biologie vegetale Universite de Montreal Montreal Quebec Canada Raymor Industries Boisbriand Quebec Canada

Cellular organelles move within the cellular volume and the effect of the resulting drag forces on the liquid causes bulk movement in the cytosol. The movement of both organelles and cytosol leads to an overall motion pattern called cytoplasmic streaming or cyclosis. This streaming enables the active and passive transport of molecules and orga- nelles between cellular compartments. Furthermore, the fusion and budding of vesicles with and from the plasma mem- brane （exo/endocytosis） allow for transport of material between the inside and the outside of the cell. In the pollen tube, cytoplasmic streaming and exo/endocytosis are very active and fulfill several different functions. In this review, we focus on the logistics of intracellular motion and transport processes as well as their biophysical underpinnings. We discuss various modeling attempts that have been performed to understand both long-distance shuttling and short-distance targeting of organelles. We show how the combination of mechanical and mathematical modeling with cell biological approaches has contributed to our understanding of intracellular transport logistics.

关键词： transport processes/kinetics cell expansion cytoskeleton dynamics protein traffic and secretion pollendevelopment.