A LARGE SCALE QUASI-CRYSTALLINE LAMELLAR LATTICE IN CHLOROPLASTS OF THE GREEN ALGA ZYGNEMA

Abstract

A quasi-crystalline lamcllar lattice was observed in chloroplasts of the filamentous grccn alga Zygnema. The latticc docs not appcar in the cclls until cultures arc at the end of the log phase of growth. Pseudograna are also present and bccomc morc numerous towards the middle of the log phasc. The three-dimcnsional latticc supcrficially resembles the configuration of cubic prolamcllar bodies but is about 10 times larger and is cntireiy different in internal structure. The lattice is composcd of onc or two apprcsscd thylakoids in a stroma matrix which is bounded on each side by a single thylakoid membrane. This multilayercd sandwich of membranes and matrix occupics a position equivalent to the singlc mcmbranc of a cubic prolamcllar body.

The vegetative arctic freshwater green alga Zygnema is insensitive to experimental UV exposure

“…Moreover, similar quantities of plastoglobules were observed in control as well as UVR-exposed samples. The special cubic-membraned structures in the chloroplasts previously observed by McLean and Pessoney (1970) and Deng and Landh (1995) in Zygnema was not observed in this study.…”

Stratum Corneum Keratin Structure, Function, and Formation: The Cubic Rod-Packing and Membrane Templating Model

“…Our tentative interpretation is that the periodic ''multicircular'' optical density pattern of Fig 7A (white square) corresponds to a continuous hyperbolic membrane structure, or ''nanoreticulum'', with cubic symmetry and small unit cell size ( $ 20 nm) (B). The similarity with the primitive (P-type) multicontinuous cubic membrane system with a large unit cell size (315 nm) in chloroplasts of green algae (McLean and Pessoney, 1970;Hyde et al, 1997, pp 277-278) (Fig 7C; Fig S4A, B) is striking (cf. Supplementary Appendix).…”

“…Fig 4); (2) It is physically as well as physiologically advantageous as it would allow for an extremely fast (phase transition) and finely tuned (curvature controlled) keratin network formation process; (3) There is evidence from other biological systems of (a) networks of protein material interwoven with membranes with hyperbolic cubic symmetry (cf. Fig S4A, B) (McLean and Pessoney, 1970), where the interwoven protein network seems to change its topology in register with the membrane network (Hyde et al, 1997, pp 277-278), and of (b) protein crystals, as well as ''amorphous protein material'', evolving directly from cubic membranes serving as crystallization templates or ''protein reservoirs'', respectively (Newcomb, 1967;Landh, 1996, p 146). (4) A candidate periodic ''template'' membrane structure with a small lattice parameter ( $ 20 nm) has been identified in native keratinocytes (cf.…”

“…Regular networks of protein material are interwoven with membranes with hyperbolic cubic symmetry in e.g., thylacoids (Fig S4A, B) (McLean and Pessoney, 1970). Despite the separate origins of the membrane and protein materials (thylacoid and stroma), the protein part seems to change its topology in register with the ''templating'' membrane part during structural transitions (Fig S4A, B) (Hyde et al, 1997, pp 277-278).…”

“…B) cubic membrane system (lattice parameter 315 nm) in chloroplasts of green algae (inset C) (cf. McLean and Pessoney, 1970;Hyde et al, 1997, pp 277-278) (cf. Supplementary Fig S4A, B).…”