title: Cell wall matrix polysaccharide distribution and cortical microtubule organization: two factors controlling mesophyll cell morphogenesis in land plants.
abstract: OBJECTIVE
  This work investigates the involvement of local differentiation of cell wall matrix polysaccharides and the role of microtubules in the morphogenesis of mesophyll cells (MCs) of three types (lobed, branched and palisade) in the dicotyledon Vigna sinensis and the fern Asplenium nidus.
  
  
  METHODS
  Homogalacturonan (HGA) epitopes recognized by the 2F4, JIM5 and JIM7 antibodies and callose were immunolocalized in hand-made leaf sections. Callose was also stained with aniline blue. We studied microtubule organization by tubulin immunofluorescence and transmission electron microscopy.
  
  
  RESULTS
  In both plants, the matrix cell wall polysaccharide distribution underwent definite changes during MC differentiation. Callose constantly defined the sites of MC contacts. The 2F4 HGA epitope in V. sinensis first appeared in MC contacts but gradually moved towards the cell wall regions facing the intercellular spaces, while in A. nidus it was initially localized at the cell walls delimiting the intercellular spaces, but finally shifted to MC contacts. In V. sinensis, the JIM5 and JIM7 HGA epitopes initially marked the cell walls delimiting the intercellular spaces and gradually shifted in MC contacts, while in A. nidus they constantly enriched MC contacts. In all MC types examined, the cortical microtubules played a crucial role in their morphogenesis. In particular, in palisade MCs, cortical microtubule helices, by controlling cellulose microfibril orientation, forced these MCs to acquire a truncated cone-like shape. Unexpectedly in V. sinensis, the differentiation of colchicine-affected MCs deviated completely, since they developed a cell wall ingrowth labyrinth, becoming transfer-like cells.
  
  
  CONCLUSIONS
  The results of this work and previous studies on Zea mays (Giannoutsou et al., Annals of Botany 2013; 112: : 1067-1081) revealed highly controlled local cell wall matrix differentiation in MCs of species belonging to different plant groups. This, in coordination with microtubule-dependent cellulose microfibril alignment, spatially controlled cell wall expansion, allowing MCs to acquire their particular shape.
authors.affiliation: Department of Botany, Faculty of Biology, University of Athens, Athens 15784, Greece and.
authors.forename: P
authors.initials: P
authors.lastname: Sotiriou
authors.affiliation: Department of Botany, Faculty of Biology, University of Athens, Athens 15784, Greece and.
authors.forename: E
authors.initials: E
authors.lastname: Giannoutsou
authors.affiliation: Department of Botany, School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Panteris
authors.affiliation: Department of Botany, Faculty of Biology, University of Athens, Athens 15784, Greece and.
authors.forename: P
authors.initials: P
authors.lastname: Apostolakos
authors.affiliation: Department of Botany, Faculty of Biology, University of Athens, Athens 15784, Greece and bgalatis@biol.uoa.gr.
authors.forename: B
authors.initials: B
authors.lastname: Galatis
mesh_terms: D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D003078:Colchicine / Q000494:pharmacology; D019669:Embryophyta / Q000187:drug effects / Q000378:metabolism*; D000939:Epitopes / Q000737:chemistry / Q000378:metabolism; D005936:Glucans / Q000378:metabolism; D058503:Mesophyll Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D009024:Morphogenesis / Q000187:drug effects; D011134:Polysaccharides / Q000378:metabolism*; D013194:Staining and Labeling; D014404:Tubulin / Q000378:metabolism
chemical_list: D000939:Epitopes; D005936:Glucans; D011134:Polysaccharides; D014404:Tubulin; C048306:callose; D003078:Colchicine
keywords: 2F4; Asplenium nidus; Callose; JIM5; JIM7; Vigna sinensis; cell contacts; cell wall; homogalacturonan.; microtubules; morphogenesis of photosynthetic cells; pectin epitopes