Latrunculin B-Induced Plant Dwarfism: Plant Cell Elongation Is F-Actin-Dependent

Abstract

Marine macrolides latrunculins are highly specific toxins which effectively depolymerize actin filaments (generally F-actin) in all eukaryotic cells. We show that latrunculin B is effective on diverse cell types in higher plants and describe the use of this drug in probing F-actin-dependent growth and in plant development-related processes. In contrast to other eukaryotic organisms, cell divisions occurs in plant cells devoid of all actin filaments. However, the alignment of the division planes is often distorted. In addition to cell division, postembryonic development and morphogenesis also continue in the absence of F-actin. These experimental data suggest that F-actin is of little importance in the morphogenesis of higher plants, and that plants can develop more or less normally without F-actin. In contrast, F-actin turns out to be essential for cell elongation. When latrunculin B was added during germination, morphologically normal Arabidopsis and rye seedlings developed but, as a result of the absence of cell elongation, these were stunted, resembling either genetic dwarfs or environmental bonsai plants. In conclusion, F-actin is essential for the plant cell elongation, while this F-actin-dependent cell elongation is not an essential feature of plant-specific developmental programs.

Simultaneous Visualization of Peroxisomes and Cytoskeletal Elements Reveals Actin and Not Microtubule-Based Peroxisome Motility in Plants,

“…Root hairs, on the other hand, develop by an actin cytoskeleton-based tip-growing mechanism. Because these cell types respond in characteristic ways to drugs that interact with the actin and microtubule cytoskeleton (Baskin et al, 1994;Bibikova et al, 1999;Mathur et al, 1999;Baluska et al, 2001), the success of our drug treatments was verified by an independent observation of altered cell morphology that were made before assessing the state of peroxisome motility in these cells. In each case, an interference with actin polymerization led to the slowing down and eventual arrest of peroxisome motility.…”

“…In Arabidopsis, these cells exhibit distinct morphological responses to microtubule-and microfilament-interacting drugs (Baskin et al, 1994;Bibikova et al, 1999;Mathur et al, 1999;Baluska et al, 2001). The specific, drug-induced morphological responses of the three cell types were observed in more than 250 cells of each kind and always correlated with the respective observations on peroxisomal motility.…”

“…Although all cells in these transgenic plants displayed fluorescent peroxisomes, for this study, we focused on three cell types exhibiting the two different modes of cell growth, namely tip and diffuse growth. These cell types, namely, trichomes and cortical and hair cells of the root, provide the additional advantage that they display clear morphological alterations upon treatment with microtubule-and actin-interacting drugs (Baskin et al1994;Mathur et al, 1999;Baluska et al, 2001). Their use introduced an independent, visually scoreable morphological criterion for ensuring that each cell where peroxisomal motility was assessed had clearly sensed and responded to the respective drug treatment.…”

Actin bundling in plants

“…Inhibitory experiments have clearly established that polar cell growth largely depends on the actin cytoskeleton (e.g. Gibbon et al, 1999;Baluska et al, 2000Baluska et al, , 2001. As they are amenable to in vitro assays and microscopic analysis, pollen tubes and root hairs emerged as attractive working models to investigate the role of the cytoskeleton during cell growth.…”

Visualization and analysis of actin cytoskeleton organization in plants

“…The actin microfilament network is essential for polar growth and intra-cellular communication: MFs mediate vesicle transport, cytoplasmic streaming, extension growth, anchoring of the nucleus, orientation of the cell division plane, gravity sensing, signalling of pathway integration, defense signalling, etc. (Baluška et al, 2001;Ketelaar et al, 2002;Klyachko, 2004;Bannigan and Baskin, 2005;Blancaflor, Wang, and Motes, 2006;Morita, 2010;Yoo et al, 2012;Blancaflor, 2013;Janda, Matoušková, Burketová, and Valentová, 2014). The actin cytoskeleton could be considered as a finer and more dynamic structure than MTs.…”