Abstract
Protein bodies (PBs) are organelles found in seeds whose main function is the storage of proteins that are used during germination for sustaining growth. PBs can also be induced to form in leaves when foreign proteins are produced at high levels in the endoplasmic reticulum (ER) and when fused to one of three tags: Zera®, elastin-like polypeptides (ELP), or hydrophobin-I (HFBI). In this study, we investigate the differences between ELP, HFBI and Zera PB formation, packing, and communication. Our results confirm the ER origin of all three fusion-tag-induced PBs. We show that secretory pathway proteins can be sequestered into all types of PBs but with different patterns, and that different fusion tags can target a specific protein to different PBs. Zera PBs are mobile and dependent on actomyosin motility similar to ELP and HFBI PBs. We show in vivo trafficking of proteins between PBs using GFP photoconversion. We also show that protein trafficking between ELP or HFBI PBs is faster and proteins travel further when compared to Zera PBs. Our results indicate that fusion-tag-induced PBs do not represent terminally stored cytosolic organelles, but that they form in, and remain part of the ER, and dynamically communicate with each other via the ER. We hypothesize that the previously documented PB mobility along the actin cytoskeleton is associated with ER movement rather than independent streaming of detached organelles.
Highlights
In plants, seeds offer highly specialized organelles for protein storage
Since recombinant fluorescent proteins targeted to the secretory pathway appeared to localize to Zera-induced protein body (PB), we co-expressed EPO with Zera-DsRed to test for an increase in accumulation of EPO in N. benthamiana leaves similar to results reported previously for elastin-like polypeptides (ELP) and HFBI PBs (Saberianfar et al, 2015)
We found that accumulation of EPO co-expressed with DsRed did not significantly change compared to EPO expressed alone (Figure 2). These results demonstrate a major difference between Zera-induced PBs and ELP or HFBI-induced PBs, both in how other proteins localize in the PBs, and in the effect on accumulation of other proteins, and lead us to further investigate differences between these PBs
Summary
Seeds offer highly specialized organelles for protein storage. These include oil bodies (OBs), protein storage vacuoles (PSVs) and protein bodies (PBs). PBs generally form within the ER lumen but they may bud off and remain in the cytosol or may be taken up by PSVs through autophagy (Levanony et al, 1992). Because of their ER origin and their significant role in protein storage, PBs represent important targets for storing recombinant proteins.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
