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Plasma Membrane - Cell Wall Continuum PCDU Seminar 2015 Stella Eggels 1 Contents • Importance of PM-CW-interactions • PM-related cell wall synthesis • PM-CW connections – Proteins involved in connections • Cytoskeleton-PM-CW Continuum: Signaling • Endocytosis of pectins – Cytokinesis 2 Importance of PM-CW-interactions • growth and cell expansion: – CW synthesis & remodeling is PM-related – structure of one depends on the other – formation of a cell plate • adaptation to environmental stimuli: – exchange of substances – transduction of signals at CW by PM-proteins • cell to cell interactions 3 PM-related cell wall synthesis – membrane composition affects location of CSC motility of CSC rate of cellulose synthesis quizlet.com/10254227/plants-ch-15taiz-flash-cards/ • transmembrane Cellulose synthase complexes (CSC): • other components: ER/Golgi PM-mediated secretion • endocytosis & recycling important for PM- & CWproduction 4 PM-CW connections • close contact due to turgor pressure • direct, physical connections: Hechtian strands – esp. at plasmodesmata – cellulose microfibrils directly or indirectly involved – different groups of proteins • PM-CW-junctions barriers against pathogen attacks 5 kimjy.gnu.kr/Lec%20Plant%20Cell%20Biol/1-Membranous%20organelles-session1.files/frame.htm Liu et al., 2015 6 Proteins involved in connections RGD-binding proteins • RGD: amino acid sequence of extracellular adhesive glycoproteins • needed for Hechtian strand formation • e.g. NDR1: RGD-like recognition motif, transmembrane domain, GPI anchor 7 GPI-anchored proteins (GAPs) • • • • GPI: surface anchor for apoplastic proteins can be released into CW e.g. COBRA Arabinogalactan proteins (AGPs) – decoration attached to CW matrix polysaccharides • Fasciclin-like AGPs 8 Plasma membrane receptors • Receptor-like kinases (RLK) • extracellular domains interact with CW-components • e.g. WAKs (wall associated kinases): bind apoplastic pectins PM-CW linker proteins and signaling: • mechanical, osmotic & pathogen stress cytoskeletal or hormonal responses 9 Cytoskeleton-PM-CW Continuum: Signaling • Mechanical signals sensed by linkers communication with cytoskeleton (esp. Actin) affect growth, differentiation, shape, cell - cell communication WAKs (+ pectins): • cytoplasmic kinase domain • B, Al bind pectin and affect cytoskeleton • receptors for endocytosis of adhesive CW pectins AGPs • bind to pectins, might interact with WAKs • mutants multiple CW-related defects Formins, Myosin VIII + Callose-Synthase 10 Handbook of Plant Science, Vol.1, Keith Roberts Endocytosis of pectins • BFA formation of dense vesicle compartments in meristematic root cells • contain pectins of inner CW-side & recycling PMproteins endocytotic origin, recycling of pectins Baluska et al. 2002 H+-ATPase PIN1 RGII-borate pectins 11 • possible effects of pectin endocytosis: – CW integrity affected growth, polarization, morphogenesis? – pectin based signaling – role in turnover of pectins in dividing cells 12 Cytokinesis • initiation and expansion of cell plate by fusion of endosomes with CW and PM material • eventually contribution of Golgi vesicles • recycling rapid, robust RGII pectin Dhonukshe et al. 2005 PIN2 13 References • • • • Baluška, F. et al. (2003). Cytoskeleton-Plasma Membrane-Cell Wall Continuum in Plants . Emerging Links Revisited. Plant Phyiology, 133(October), 482–491. Dhonukshe, P. et al. (2006). Endocytosis of Cell Surface Material Mediates Cell Plate Formation during Plant Cytokinesis. Developmental Cell, 10(1), 137–150. Liu, Z. et al. (2015). At the border: the plasma membrane-cell wall continuum. Journal of Experimental Botany, 66(6), 1553–1563. Palme, K. et al. (2002). F-actin-dependent endocytosis of cell wall pectins in meristematic root cells. Insights from brefeldin A-induced compartments. Plant Physiology, 130(1), 422–431. 14 Thank you! 15