Plant Vacuoles

Abstract

Most plant cells contain one or several vacuoles, which may occupy up to 95% of the cellular space. The vacuoles often appear empty under a light microscope (hence their name), except when they contain pigments or precipitated substances. The vacuole is delimited from the cytosol by the vacuolar membrane, which is also called tonoplast. Vacuoles are compartments of the secretory pathway derived from the endoplasmic reticulum and the Golgi apparatus. Their function include the storage of ions, sugars, proteins and xenobiotics. They also participate in volume changes during growth and development, movements such as stomata opening and closing and the maintenance of internal turgor pressure for the mechanical stiffness of green tissues. Although most plant cells have a single central vacuole, some cells have two different vacuoles with different contents and functions. Vacuole biogenesis is a complicated process involving several intermediate compartments, vesicle trafficking and fusion. Key Concepts: The large central vacuole plays an important role in temporary storage of metabolites, thus allowing keeping the metabolite levels constant in the cytosol. Plant cells can harbour two different types of vacuoles with different contents and functions. Vacuoles are compartments of the secretory pathway and derive their membrane (tonoplast) and protein content from the ER via the Golgi apparatus and pre‐vacuolar compartments. Some storage vacuoles may however derive directly from the ER. Toxic compounds are preferentially stored in the large central vacuole, since in this compartment they do not interfere with plant metabolism.

Production of the Main Celiac Disease Autoantigen by Transient Expression in Nicotiana benthamiana

“…Increased vacuolar accumulation was also observed for human alpha-mannosidase, whose N-terminal sequence sorted it directly to the vacuole bypassing the Golgi apparatus ( De Marchis et al, 2013 ). It is believed that VSSs are necessary for post-Golgi sorting to vacuoles and that the traffic pathway can affect foreign protein stability since the pH varies along the secretory pathway ( Neuhaus and Martinoia, 2011 ; Shen et al, 2013 ). The different data published for vacuolar sorted foreign proteins, indicate that reaching a stable accumulation in vacuoles is more dependent on the nature of the foreign protein than the sorting signal used.…”