Actin Depolymerization Affects Stress-Induced Translational Activity of Potato Tuber Tissue1

Abstract

Changes in polymerized actin during stress conditions were correlated with potato (Solanum tuberosum L.) tuber protein synthesis. Fluorescence microscopy and immunoblot analyses indicated that filamentous actin was nearly undetectable in mature, quiescent aerobic tubers. Mechanical wounding of postharvest tubers resulted in a localized increase of polymerized actin, and microfilament bundles were visible in cells of the wounded periderm within 12 h after wounding. During this same period translational activity increased 8-fold. By contrast, low-oxygen stress caused rapid reduction of polymerized actin coincident with acute inhibition of protein synthesis. Treatment of aerobic tubers with cytochalasin D, an agent that disrupts actin filaments, reduced wound-induced protein synthesis in vivo. This effect was not observed when colchicine, an agent that depolymerizes microtubules, was used. Neither of these drugs had a significant effect in vitro on run-off translation of isolated polysomes. However, cytochalasin D did reduce translational competence in vitro of a crude cellular fraction containing both polysomes and cytoskeletal elements. These results demonstrate the dependence of wound-induced protein synthesis on the integrity of microfilaments and suggest that the dynamics of the actin cytoskeleton may affect translational activity during stress conditions.

Chilling and Freezing Stresses in Plants: Cellular Responses and Molecular Strategies for Adaptation

“…Mazars et al report that disruption of microtubules and actine micro filaments stimulates the cold-induced Ca 2 + influx in tobacco protoplasts [46]. Similar results were reported on K+ channel activity in stomatal opening and in mechanical stress signalling [47,48]. The presence in the aminoacid sequence of AKTl, putatively encoding a K+ channel, of an ankyrin-like repeat supports the idea of a direct interaction between ion channel and cytoskeleton [49].…”

Transcriptional profiling of sunflower plants growing under low temperatures reveals an extensive down-regulation of gene expression associated with chilling sensitivity

“…Many environmental factors have also been found to affect the expression of many genes involved in translation activity and protein synthesis in different plant species. This includes, for example, ultraviolet radiation (Casati and Walbot, 2003), low-oxygen stress (Morelli et al, 1998), nitrate uptake (Wang et al, 2004), salinity (Ozturk et al, 2002), and light conditions (Ma et al, 2001). Taken together, these results indicate that changes in growing temperatures could be one of several environmental factors contributing to changes in translation activity and protein synthesis.…”

A Role for F-Actin in Hexokinase-Mediated Glucose Signaling

“…The association of some cellular polysomes and other translational components with the cytoskeleton has been recognized for a number of years in plants as well as animals (Davies et al, 1998). For example, the loss of fine mesh actin filaments in potato (Solanum tuberosum) tubers is associated with the loss of wound-induced message translation activity under conditions of low O 2 (Morelli et al, 1998). Researchers have been able to isolate four defined populations of polysomes: free, membrane bound, actin bound, and actin membrane bound polysomes.…”