Protein Storage Vacuoles Originate from Remodeled Preexisting Vacuoles in Arabidopsis thaliana

Abstract

Protein storage vacuoles (PSV) are the main repository of protein in dicotyledonous seeds, but little is known about the origins of these transient organelles. PSV are hypothesized to either arise de novo or originate from the preexisting embryonic vacuole (EV) during seed maturation. Here, we tested these hypotheses by studying PSV formation in Arabidopsis () embryos at different stages of seed maturation and recapitulated this process in Arabidopsis leaves reprogrammed to an embryogenic fate by inducing expression of the transcription factor. Confocal and immunoelectron microscopy indicated that both storage proteins and tonoplast proteins typical of PSV were delivered to the preexisting EV in embryos or to the lytic vacuole in reprogrammed leaf cells. In addition, sectioning through embryos at several developmental stages using serial block face scanning electron microscopy revealed the 3D architecture of forming PSV. Our results indicate that the preexisting EV is reprogrammed to become a PSV in Arabidopsis.

A Diverse Membrane Interaction Network for Plant Multivesicular Bodies: Roles in Proteins Vacuolar Delivery and Unconventional Secretion

“…The plant LVs contain acid hydrolases playing an important role in multiple biological processes such as protein turnover, abiotic, and biotic stresses defense, and keeping cellular homeostasis (Tan et al, 2019), whereas the PSVs mainly function to store proteins (Jiang et al, 2001). Interestingly, PSVs can convert into LVs during seed germination while LVs can also be replaced by PSVs in leaf cells, although the detailed mechanism of the LV-PSV transition is still largely unknown (Jiang et al, 2001;Feeney et al, 2018;Kwon et al, 2018). The soluble proteins in LVs are mainly transported by the PVC/MVB-mediated vacuolar pathway, while the storage proteins in PSVs are transported by diverse routes.…”

“…Compared to the tremendously diverse roles of the MVBs in mammals and yeast, the reported functions of the PVC/MVBs in plants remain somewhat limited. State-of-the-art microscopy technology, such as super-resolution fluorescence microscopy with 3D structures in living cells, light-sheet microscopy for 4D imaging, as well as 3D TEM and correlative light-electron microscopy (CLEM) approaches (Feeney et al, 2018;Wang et al, 2019), can be expected to be useful tools for the analysis of endosomal structure and trafficking when plants are placed under multiple environments. This will undoubtedly bring new insights into our understanding of the PVC/MVB membrane interaction network and their associated functions.…”

Aquaporins influence seed dormancy and germination in response to stress

“…TIP3;1 and TIP3;2 (henceforth collectively referred to as TIP3 ) are highly expressed during seed maturation and early during germination. TIP3 are located on the tonoplast of seed protein storage vacuoles (PSV; Feeney, Kittelmann, Hawes, & Frigerio, ; Gattolin et al, ; Hunter, Craddock, Di Benedetto, Roberts, & Frigerio, ) and at the plasma membrane (Gattolin et al, ). In embryos from mature seeds, the protein expression patterns of TIP3;1 and TIP3;2 overlap (Gattolin et al, ).…”

Serial block face scanning electron microscopy in cell biology: Applications and technology

“…The knife can also quickly remove a greater volume of material than the ion beam of the FIBSEM, meaning that larger volumes of tissue can feasibly be scanned (figure 3). Both techniques can reach a minimum X,Y pixel size of around 3-5nm (Daum et al, 2017;Feeney et al, 2018) however voxel size in the Zdirection is at best 20nm in SBFSEM (Chen et al, 2017) (a limit set by the cutting of the knife) whereas FIBSEM allows the milling of arbitrarily thin sections. Compared to ssTEM, both FIBSEM and SBFSEM sacrifice ultimate resolution in exchange for greater ease of use and reliability: both block face techniques allow the user to leave the microscope on 'autopilot' once a run has been initiated (assuming there are no problems encountered with cutting/milling or imaging), and thus the total work hours needed to produce a complete dataset are vastly reduced.…”