Radial endoplasmic reticulum arrays co-localize with radial F-actin in polarizing cells of brown algae

Abstract

The organisation of the endoplasmic reticulum (ER) was examined in branching thallus cells and germinating cells derived from regenerated protoplasts (protoplast derived cells; PDCs) of Macrocystis pyrifera gametophytes by both immunofluorescent labelling of the HDEL sequence and vital staining with DiOC 6 (3), and in branching thallus cells of Splachnidium rugosum and Choristocarpus tenellus with DiOC 6 (3) staining. In M. pyrifera and S. rugosum cells, distinctive cortical ER configurations with a clear radial arrangement were found at sites where a protrusion will emerge, while branching C. tenellus cells had a cortical ER patch from which a few linear ER elements expanded towards the rest of the cell. Examination of the organization of actin filaments (AFs) revealed similar radial AF structures at the site of the future protrusion, while the microtubule (Mt) organisation did not show any similar characteristic structure at the protrusion site. Latrunculin B inhibited germination in M. pyrifera PDCs, and the treated cells lacked radial ER or AF configurations. Treatment with taxol did not affect the germination process or the radial configurations. The structural similarity and the temporal and spatial coincidence of the ER and AF configurations combined with the inhibitor experiments lead to the hypothesis that ER, in conjunction with AFs, is implicated in the fixation of the polar axis in brown algal cells. The existence of characteristic ER and AF configurations in polarising cells of the three species suggests that they are a common characteristic of the brown algae.

Formation of an endoplasmic reticulum ring associated with acetylated microtubules in the angiosperm preprophase band

“…By immunogold labeling, it has been confirmed that these proteins are located in the lumen of the ER and the nuclear envelope [Napier et al, 1992]. For this reason, this antibody is widely and successfully used for the immunodetection of ER in plant cells [Zachariadis et al 2003; Varvarigos et al, 2007].…”

“…ER was immunolabeled with the monoclonal antibody 2E7 that recognizes the luminar ER proteins having the C‐terminal HDEL sequence and specifically marks the plant ER [Napier et al, 1992]. This antibody has already been successfully used for ER immunolocalization in various plant cell types [Zachariadis et al, 2001, 2003; Varvarigos et al, 2007; Giannoutsou et al, 2011]. In this study, leaf and root cells have been examined, since at least in Z. mays , acetylated tubulin is reportedly present in leaf but not in root cells [Wang et al, 2004].…”

Desiccation Stress Causes Structural and Ultrastructural Alterations in the Aeroterrestrial Green Alga Klebsormidium Crenulatum (Klebsormidiophyceae, Streptophyta) Isolated From an Alpine Soil Crust1

“…2010), K. crenulatum exhibited high respiratory activity, even at elevated temperatures (up to 40°C). We therefore investigated the appearance and number of mitochondria by application of DIOC 6 , a dye that has been successfully used for ER and mitochondrial visualization in green algae (Hayashi and Ueda 1989, Menzel 1994, Varvarigos et al. 2007).…”

Asymmetric microtubule arrays organize the endoplasmic reticulum during polarity establishment in the brown alga Silvetia compressa

“…To investigate the possible spatial relationship between microtubules and endoplasmic reticulum, zygotes were double labeled for microtubules and endoplasmic reticulum. A monoclonal antibody to the endoplasmic reticulum retention signal (HDEL), which has been used for successful localization studies in other species of brown algae [Varvarigos et al,2007], was used to visualize endoplasmic reticulum. Both HDEL and microtubule signal intensity appeared uniform at 2 h AF, but as polarization proceeded microtubule and HDEL asymmetry increased (Fig.…”