Implication of actin in the uptake of sucrose and valine in the tap root and leaf of sugar beet

Abstract

Actin microfilaments (F-actin) are major components of the cytoskeleton essential for many cellular dynamic processes (vesicle trafficking, cytoplasmic streaming, organelle movements). The aim of this study was to examine whether cortical actin microfilaments might be implicated in the regulation of nutrient uptake in root and leaf cells of Beta vulgaris. Using antibodies raised against actin and the AtSUC1 sucrose transporter, immunochemical assays demonstrated that the expression of actin and a sucrose transporter showed different characteristics, when detected on plasma membrane vesicles (PMVs) purified from roots and from leaves. The in situ immunolabeling of actin and AtSUC1 sites in PMVs and tissues showed their close proximity to the plasma membrane. Using co-labeling in protoplasts, actin and sucrose transporters were localized along the internal border and in the outermost part of the plasma membrane, respectively. This respective membrane co-localization was confirmed on PMVs and in tissues using transmission electronic microscopy. The possible functional role of actin in sucrose uptake (and valine uptake, comparatively) by PMVs and tissues from roots and leaves was examined using the pharmacological inhibitors, cytochalasin B (CB), cytochalasin D (CD), and phalloidin (PH). CB and CD inhibited the sucrose and valine uptake by root tissues in a concentration-dependent manner above 1 μM, whereas PH had no such effect. Comparatively, the toxins inhibited the sucrose and valine uptake in leaf discs to a lesser extent. The inhibition was not due to a hindering of the proton pumping and H + -ATPase catalytic activity determined in PMVs incubated in presence of these toxins. | INTRODUCTIONThe plant cytoskeleton is generally considered to consist of distinct components, for example, microtubules, microfilaments, and intermediary filaments. The microfilament system has been well characterized in plant cells. In particular, actin microfilaments (MFs or F-actin) are highly organized and major components of the cytoskeleton, and are essential for many cellular processes, including division, expansion, and differentiation (Higaki, Sano, & references therein, Hussey et al., 2006, and references therein). Further, dynamic processes, such as vesicle trafficking, cytoplasmic streaming, and organelle movements, are also controlled by MFs (Kandasamy & Meagher, 1999;Van Gestel et al., 2002). Moreover, the actin cytoskeleton is implicated in plant defense against pathogens (Hardham et al., 2007;Tian et al., 2009), and MF modification is also observed during elicitor-induced vacuolar disintegration in programmed cell death (Higaki, Goh, et al., 2007). Plants express multiple actin isoforms, which are dependent on tissues, organs, and stage of development, suggesting that individual isoforms play specific roles in cells, presumably through interactions with specific actin binding proteins (Kijima et al., 2016). Actin and some of the associated proteins are well conserved in plants and animals (Abu-Abied et al., 2006).

Illumina Sequencing and Metabolomic Analysis Explored the Effects of the Mixed Silage of Rice Straw and Chinese Cabbage Waste on Fecal Microorganisms and Metabolites in Hu Sheep

“…Amino acids are important for microbial growth and metabolism, and are key components of protein and peptide synthesis and regulate several metabolic pathways [44]. L-valine enters the tricarboxylic acid cycle to provide energy and has important roles in protein synthesis, cell proliferation, and signaling pathway activation [45,46]. NAG is an important allosteric activator of carbamoyl phosphate synthase.…”