Lessons from optical tweezers: quantifying organelle interactions, dynamics and modelling subcellular events

Abstract

Optical tweezers enable users to physically trap organelles and move them laterally within the plant cell. Recent advances have highlighted physical interactions between functionally related organelle pairs, such as ER-Golgi and peroxisome-chloroplast, and have shown how organelle positioning affects plant growth. Quantification of these processes has provided insight into the force components which ultimately drive organelle movement and positioning in plant cells. Application of optical tweezers has therefore revolutionised our understanding of plant organelle dynamics.

Communications Between the Endoplasmic Reticulum and Other Organelles During Abiotic Stress Response in Plants

“…Arabidopsis lacks a homolog of Nvj1 or Ltc1 but contains >100 armadillo repeat proteins (Sharma et al, 2014) and five tricalbin homologs known as AtSYTA-E or AtSYT1–5 (Craxton, 2004). Live cell imaging of fluorescently tagged ER/tonoplast-localized proteins coupled with optical tweezers (Sparkes, 2018) could reveal potential ER-vacuole contact sites and their dynamic changes in response to environmental stresses. Given the widespread occurrence of SMP-containing proteins at multiple MCSs in yeast and mammalian cells (Toulmay and Prinz, 2012), identification of a plant ER-vacuole tethering complex might be facilitated by confocal microscopic examination of fluorescently tagged AtSYT1–5 followed by biochemical studies of an AtSYT localized at the ER-vacuole contact sites.…”

A moonlighting role for enzymes of glycolysis in the co-localization of mitochondria and chloroplasts

“…The association of organelles has previously been observed and is often postulated to aid metabolic pathways that span organelles, such as photorespiration and nitrogen assimilation, and may also be beneficial for biochemical efficiency 15 – 18 . In addition to the clear metabolic intimacy of the organelles of the plant cell, mitochondria and chloroplasts have frequently been observed to spatially colocalize—a feature that has, among other considerations, been hypothesized to be important to ensure energy-use efficiency 16 , 19 , 20 . The direct interaction between mitochondrial and chloroplast outer membranes has been demonstrated using transmission electron micrographs (TEMs) of parenchyma cells from Citharexylum myrianthum 21 .…”

“…The direct interaction between mitochondrial and chloroplast outer membranes has been demonstrated using transmission electron micrographs (TEMs) of parenchyma cells from Citharexylum myrianthum 21 . It has also become apparent that membrane microdomains may be important for organelle trafficking, cellular signaling, and organelle tethering 16 , 19 , and it has been speculated that metabolite exchange between organelles could be regulated by these microdomains, which could involve direct channeling of molecules and synchronization without the necessity for cytosolic involvement 15 , 18 , 19 . Following this theory, the exchange of metabolites between respiration and photosynthesis would be more efficient.…”

Quantitative analysis of plant ER architecture and dynamics

“…These features are visible at the electron microscopy (EM) level 28 and have been characterised with nanometre resolution using TEM and electron tomography 12 . They have been identified in living cells using persistency analysis 5,29–34 , and following manipulation using optical tweezers 22,29,35 . Increasing the expression of certain proteins, such as VAP27 and SYT1, modulate the number and size of EPCS, and also affect the stability of the ER network 27,33,34 .…”