Diameters of microtubules change during rotation of the lipotubuloids of Ornithogalum umbellatum stipule epidermis as a result of varying protofilament monomers sizes and distance between them

Abstract

Microtubules in lipotubuloids of the Ornithogalum umbellatum stipule epidermis cells change their diameters depending on the motion of the cytoplasmic domains rich in microtubules and lipid bodies. Microtubules fixed during rotary and progressive motion of the lipotubuloids composed of the same number of protofilaments fall into two populations - wide (43-58 nm) and narrow (24-39 nm) in size. Following blockage of the motion with 2,4-dinitrophenol (DNP), the range of this diversity is smaller, microtubules become a medium-sized population (34-48 nm). When DNP is removed and the motion reactivated, 2 populations of microtubules reappear. Analysis of the structure of the microtubule wall revealed that changes in the microtubule diameters resulted from varying distances between the adjacent protofilaments, and stretching and compression of tubulin subunits in the protofilaments. A supposition has been put forward that the changes in the sizes of O. umbellatum microtubule diameters: 1) are connected with the interactions between microtubules and actin microfilaments lying along these microtubules; 2) can be the driving force of the rotary motion of lipotubuloids.

Lipotubuloids - Structure and Function

“…3) (Kwiatkowska et al, 2005). A hypothesis has been put forward that interaction of actin filaments with microtubules may determine the transformation of wide microtubules into narrow ones and vice versa (Kwiatkowska et al, 2009). Microtubules of varying sizes were observed in vitro as a result of tubulin co-sedimentation in the presence of actin and myosin Va (Cao et al, 2004).…”

“…14), two populations were revealed: wide (43-58 nm) and narrow (24-39 nm). In the lipotubuloids in the ovary epidermis which move less dynamically the number of wide microtubules is smaller (Kwiatkowska et al, 2006) than in the fast-moving lipotubuloids present in stipule (Kwiatkowska et al, 2009). The microtubule diameter depends on the varying number of protofilaments which form them, the bigger the number the greater the diameter (Fig.…”

“…In the wider microtubules both these parameters are greater and vice versa (Kwiatkowska et al, 2009). All the above proves flexibility of microtubules in vivo depending on their functional status.…”

“…13. A scheme of a lipotubuloid in an epidermal cell of O. umbellatum stipule which has turned around (several times) within 10-12 s, changing its direction and axis without a change in cellular location; c -cytoplasm, l -lipotubuloid, n -nucleus, v -vacuole, long arrows -the direction of lipotubuloid rotation, short arrows -direction of cytoplasm movement (Kwiatkowska et al, 2009). Moreover, it turned out that microtubules of lipotubuloids differ in diameter (Fig.…”

“…15. A -A scheme of microtubules whose width depends on the number of filaments; B -a graph presenting two microtubule populations in the control and after DNP removal, and one microtubule population after DNP application (Kwiatkowska et al, 2009). …”