CELL‐WALL DEVELOPMENT AND BIPOLAR GROWTH IN THE DESMID PENIUM MARGARITACEUM (ZYGNEMATOPHYCEAE, STREPTOPHYTA). ASYMMETRY IN A SYMMETRIC WORLD¹

Abstract

Cell-wall (CW) development in the desmid Penium margaritaceum (Ehrenb.) Bréb. was studied using immunofluorescence labeling of living cells with the monoclonal antibodies (mAbs) JIM5 and JIM7, which recognize unesterified and methyl-esterified homogalacturonan (HG), respectively. During cell expansion, HG was secreted in a high-esterified form at a narrow band, called the HG secretion band or HGSB, at the isthmus or the polar tip of a daughter semicell. As newly secreted HG is displaced outward on the cell surface, deesterification and subsequent calcium (Ca(2+) )-complexing occurred to yield a rigid covering. HG secretion and CW/cell expansion were reversibly inhibited by dark, brefeldin A (BFA), and incubation in 0.24-0.36 M sucrose but were not altered by treatment with actin/microfilament drugs. The HGSB was detected near the nucleus during most cell-cycle events. Centrifugation displaced the nucleus away from the HGSB, but HG synthesis was not affected. HGSB activity was preceded by, and coordinated with, Calcofluor labeling, which suggests that cellulose production in CW/cell-expansion sites was critical to expansion control. In many first-cell-division products, asymmetric patterning of HG was noted in the CW. These asymmetric patterns most likely were a result of timing mechanisms and displacement of the nucleus-HGSB during the cell cycle.

Pectin Metabolism and Assembly in the Cell Wall of the Charophyte Green Alga Penium margaritaceum

“…margaritaceum is a cylindrical unicell, consisting of two semicells attached at a central isthmus zone (Fig. 1A), which is the site of active wall expansion during cell growth and division (Domozych et al, 2009). This simple morphology and associated morphogenesis program allow for convenient imaging of P. margaritaceum cell wall architecture that, in this study, was assessed using variable pressure scanning electron microscopy (VPSEM), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM).…”

“…Immunogold labeling using an expanded set of mAbs that recognize different pectin epitopes and TEM imaging were employed to generate a more detailed spatial map of pectin distribution and dynamics than we have described previously (Domozych et al, 2007b(Domozych et al, , 2009). The mAb JIM5, which recognizes HG with a relatively low degree of methylesterification (Clausen et al, 2003), labeled both the OL lattice and ML (Fig.…”

“…Live cell labeling of cells with mAbs followed the protocol of Domozych et al (2009Domozych et al ( , 2011. The antibody labeling buffer, except for 2F4, consisted of WHM (pH 7.2; contains 250 mM CaCl 2 ), and the blocking buffer was WHM with 0.5% (w/v) bovine serum albumin (Sigma-Aldrich).…”

Phylogeny and Molecular Evolution of the Green Algae

“…Although some cell wall components do appear to be land plant innovations, cell wall evolution after the colonization of land appears to be characterized mostly by the elaboration of a pre-existing set of cell wall polysaccharides and the enzymes that synthesize them (e.g. cellulose synthase and wall-remodelling enzymes), rather than substantial innovation (Roberts & Roberts, 2004;Domozych et al, 2007;Van Sandt et al, 2007;Eder et al, 2008;Fry et al, 2008;Domozych et al, 2009;Yin et al, 2009;Popper & Tuohy, 2010;Popper et al, 2011).…”

Cell Wall Growth and Modulation Dynamics in a Model Unicellular Green Alga—Penium margaritaceum: Live Cell Labeling with Monoclonal Antibodies

“…Once secreted, the HG displaces the older cell wall complex outward toward each pole. During this process, the HG is de-esterified, presumably by a PME, and subsequently complexes with Ca 2+ to yield the reticulated outer cell wall layer [16]. Live cell labeling of Penium affords multiple and exciting opportunities to examine both the qualitative and quantitative aspects of HG and wall dynamics during cell development and the effects of specific altering agents on wall synthesis.…”