NET4 modulates the compactness of vacuoles in Arabidopsis thaliana

Abstract

The dimension of the plants largest organelle -the vacuole, plays a major role in defining cellular elongation rates. The morphology of the vacuole is controlled by the actin cytoskeleton but the mechanistic connection between them remains largely elusive. Recently, the NETWORKED (NET) family of membrane-associated, actin-binding proteins has been identified and represent potential candidates to impact on vacuolar morphology. Here, we show that NET4A localizes to highly constricted regions in the vacuolar membrane and contributes to the compactness of the vacuole. Using genetic interference, we found that deregulation of NET4 abundance impacts on vacuole morphogenesis and overexpression leads to more compact vacuoles. We moreover show that the NET4A-induced changes in vacuolar shape correlates with reduced cellular and organ growth in Arabidopsis thaliana. Our results demonstrate that NET4 modulates the compactness of vacuoles and reveal higher complexity in the regulation of actin-reliant vacuolar morphology. Results and Discussion

The TOR–Auxin Connection Upstream of Root Hair Growth

“…The expanding root hair tip is almost fully filled with the vacuole, surrounded by a thin layer of highly polarized cytoplasm [ 8 ]. Vacuolar morphology has to date been extensively studied during the elongation processes of cells in the primary root tip, where it is crucial to maintain the expansion of the elongating cell without investing excessive resources to build up cytoplasmic content and stability [ 94 , 196 , 197 , 198 , 199 , 200 ]. It highly depends on intracellular auxin concentration [ 23 , 82 , 201 ] and signaling pathways partially regulated by FER [ 202 , 203 ].…”

Membrane contact sites and cytoskeleton‐membrane interactions in autophagy

“…The NET4 subfamily of actin‐membrane contact site proteins is emerging as a regulator of actin‐vacuole contact sites. NET4 proteins bind actin at the tonoplast [5,8,40], and may function to regulate vacuolar occupancy [40]. NET4 proteins have recently been characterised as downstream effectors of RabG3, which recruit NET4 to the tonoplast to mediate actin‐driven vacuolar remodelling in response to extracellular pathogen perception [8].…”

Resolving the Cohenian paradox in judicial probability theory

“…Vacuolar size is controlled by the phytohormone auxin, which restricts the rate of cellular expansion (Löfke et al, 2015). Auxin interferes with the delivery and fusion of vesicles to the tonoplast, as well as with actin/myosin-dependent constriction of the vacuole, contributing to the volume of the vacuole and its cellular occupation (Löfke et al, 2015;Scheuring et al, 2016;Kaiser et al, 2019). A cell wall sensing mechanism allows for the alignment of cell wall acidification/loosening with intracellular vacuole expansion, consequently ensuring cytosol homeostasis required for rapid cell expansion (Dünser et al, 2019;reviewed in Herger et al, 2019).…”