title: Differential coloring reveals that plastids do not form networks for exchanging macromolecules.
abstract: Stroma-filled tubules named stromules are sporadic extensions of plastids. Earlier, photobleaching was used to demonstrate fluorescent protein diffusion between already interconnected plastids and formed the basis for suggesting that all plastids are able to form networks for exchanging macromolecules. However, a critical appraisal of literature shows that this conjecture is not supported by unequivocal experimental evidence. Here, using photoconvertible mEosFP, we created color differences between similar organelles that enabled us to distinguish clearly between organelle fusion and nonfusion events. Individual plastids, despite conveying a strong impression of interactivity and fusion, maintained well-defined boundaries and did not exchange fluorescent proteins. Moreover, the high pleomorphy of etioplasts from dark-grown seedlings, leucoplasts from roots, and assorted plastids in the accumulation and replication of chloroplasts5 (arc5), arc6, and phosphoglucomutase1 mutants of Arabidopsis thaliana suggested that a single plastid unit might be easily mistaken for interconnected plastids. Our observations provide succinct evidence to refute the long-standing dogma of interplastid connectivity. The ability to create and maintain a large number of unique biochemical factories in the form of singular plastids might be a key feature underlying the versatility of green plants as it provides increased internal diversity for them to combat a wide range of environmental fluctuations and stresses.
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G2W1, Canada.
authors.forename: Martin H
authors.initials: MH
authors.lastname: Schattat
authors.forename: Sarah
authors.initials: S
authors.lastname: Griffiths
authors.forename: Neeta
authors.initials: N
authors.lastname: Mathur
authors.forename: Kiah
authors.initials: K
authors.lastname: Barton
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wozny
authors.forename: Natalie
authors.initials: N
authors.lastname: Dunn
authors.forename: John S
authors.initials: JS
authors.lastname: Greenwood
authors.forename: Jaideep
authors.initials: J
authors.lastname: Mathur
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism; D001692:Biological Transport; D003116:Color; D003624:Darkness; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure; D008164:Luminescent Proteins / Q000378:metabolism; D046911:Macromolecular Substances / Q000378:metabolism*; D008561:Membrane Fusion; D008928:Mitochondria / Q000378:metabolism; D020675:Peroxisomes / Q000378:metabolism; D055668:Photochemical Processes; D010858:Pigmentation / Q000502:physiology*; D018087:Plastids / Q000378:metabolism* / Q000648:ultrastructure; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism; D014026:Nicotiana / Q000166:cytology / Q000378:metabolism
chemical_list: D008164:Luminescent Proteins; D046911:Macromolecular Substances