The tannosome is an organelle forming condensed tannins in the chlorophyllous organs of Tracheophyta

Abstract

The presence of the three different chloroplast membranes inside vacuolar accretions that constitute the typical form of tannin storage in vascular plants was established in fresh tissues as well as in purified organelles, using several independent methods. Tannins are polymerized in a new chloroplast-derived organelle, the tannosome. These are formed by pearling of the thylakoids into 30 nm spheres, which are then encapsulated in a tannosome shuttle formed by budding from the chloroplast and bound by a membrane resulting from the fusion of both chloroplast envelopes. The shuttle conveys numerous tannosomes through the cytoplasm towards the vacuole in which it is then incorporated by invagination of the tonoplast. Finally, shuttles bound by a portion of tonoplast aggregate into tannin accretions which are stored in the vacuole. Polymerization of tannins occurs inside the tannosome regardless of the compartment being crossed. A complete sequence of events apparently valid in all studied Tracheophyta is described.

Morphological, histological and ultrastructural features of osmophores and nectary of Bulbophyllum wendlandianum (Kraenzl.) Dammer (B. section Cirrhopetalum Lindl., Bulbophyllinae Schltr., Orchidaceae)

“…The tannin-like material found in cells of studied tepals offers protection against pathogens, herbivores and UV radiation. Tannins are described in cell suspension cultures and calluses from various gymnosperms (Constabel 1969;Chafe and Durzan 1973;Parham and Kaustinen 1977) or in petals (Ochir et al 2010), forming in tannosomes (Brillouet et al 2013). The stelidia, with no secretion on the very undulated cuticle, do not emit fragrance.…”

Photosynthesis under artificial light: the shift in primary and secondary metabolism

“…Interestingly, re-etiolation provides adequate conditions for the production of white asparagus, chicory or seakale [30]. In tea leaves, the re-etiolation increases the content of volatiles (aroma), especially volatile phenylpropanoids/benzenoids and several amino acids, including L-phenylalanine [31], suggesting the activation of a plastid-located shikimate pathway [32].…”

“…They are used in repairing mechanisms [36], shielding [37], reactive oxygen species (ROS) quenching [37] or the production of storage compounds [38]. The synthesis of the metabolites takes place in plastids (terpenoids [38]) or involves them ( phenylpropanoids [32]). Typical examples are medicinal plants and herbs of pharmaceutical importance such as mint (Mentha sp.)…”

Formation of vacuolar tannin deposits in the chlorophyllous organs of Tracheophyta: from shuttles to accretions

“…A large body of evidence argues that tannins are formed in recently described thylakoid-derived organelles, the tannosomes, which are packed in membrane-bound shuttles (Brillouet et al 2013); it has been suggested that shuttles agglomerate into tannin accretions. The aim of the study was to describe the ontogenesis of tannin accretions in members of the Tracheophyta.…”