The mysterious life of the plant trans‐Golgi network: advances and tools to understand it better

Abstract

By being at the interface of the exocytic and endocytic pathways, the plant trans-Golgi network (TGN) is a multitasking and highly diversified organelle. Despite governing vital cellular processes, the TGN remains one of the most uncharacterized organelle of plant cells. In this review, we highlight recent studies that have contributed new insights and to the generation of markers needed to answer several important questions on the plant TGN. Several drugs specifically affecting proteins critical for the TGN functions have been extremely useful for the identification of mutants of the TGN in the pursuit to understand how the morphology and the function of this organelle are controlled. In addition to these chemical tools, we review emerging microscopy techniques that help visualize the TGN at an unpreceded resolution and appreciate the heterogeneity and dynamics of this organelle in plant cells. Proteins and chemicals with action at the TGN/EE: what are we discovering?

Plant Golgi ultrastructure

“…However, double labeling experiments with unspecific (the styryl dye FM4‐64) and specific (the BRI1‐YFP, brassinosteroid insensitive1 receptor) endocytic tracers and the fluorescent TGN markers (VHA‐a1‐RFP; ST‐GFP) have convincingly demonstrated that the TGN also acts as an endocytic compartment and functions as the early endosome (EE) in plants (Viotti et al ., 2010). The TGN/EE has a discrete set of marker proteins and is equipped with a V‐ATPase type proton pump which serves to acidify this organelle (for details, see the recent reviews Elliott et al ., 2020; Renna & Brandizzi, 2020).…”

An Update on the Key Factors Required for Plant Golgi Structure Maintenance

“…Plant TGN/EE, comprising of blebbing, tubular-reticular membranes with clathrin-coated vesicles (CCV), is a distinct organelle arises from cisternal maturation of the trans most Golgi cisterna (Golgi-associated TGNs, GA-TGNs), while GI-TGNs (Golgi-released independent TGNs) derived from GA-TGN are away and behave independently from the Golgi apparatus ( Viotti et al, 2010 ; Kang et al, 2011 ; Uemura et al, 2014 , 2019 ). TGNs are sub-compartmentalized molecularly and functionally ( Heinze et al, 2020 ; Renna and Brandizzi, 2020 ), and most recently, two subregions of a single TGN, namely, the secretory trafficking zone and the vacuolar trafficking zone, responsible for distinct cargo sorting are proposed ( Shimizu et al, 2021 ). Application of specific Vacuolar H + -ATPase (VHA-ATPase) inhibitor Concanamycin A causes the loss of TGN/EE identity possibly by increasing its lumenal pH, this leads to vacuolation of TGN/EE, Golgi cisternae bending, and Golgi fragmentation in BY-2 cells ( Robinson et al, 2004 ).…”

Complex roles of Rabs and SNAREs in the secretory pathway and plant development: a never‐ending story

“…As highlighted by Renna and Brandizzi (2020), the numerous tools developed (reverse genetics, proteomics, chemical inhibitors, superresolution live‐cell imaging etc.) together with lipidomics (Wattelet‐Boyer et al ., 2016) are now at hand to unravel the different functions of the TGN, to determine all the key actors and functional machineries in the different subdomains involved in cargo sorting and transport, and finally to investigate the homeostatic regulation of the TGN in various environmental conditions.…”