INFLUENCE OF GRAVITY ON THE CYTOSKELETON AND THE DETERMINATION OF THE DIVISION PLANE
IN PLANTS (TUBUL/TUBUL-2), TWO INVESTIGATIONS
Research Area: Plant Biology
Expedition(s): 8, 9 and 13
Principal Investigator(s): ● Annie Emons, Wageningen University, Wageningen,
Netherlands
RESEARCH OBJECTIVES
The main scientific objective of the Influence of Gravity on the Cytoskeleton and the
Determination of the Division Plane in Plants (Tubul/Tubul-2), Two Investigations experiment is
to study the effect of weightlessness over time on the microtubule cytoskeleton of individual
walled plant cells (Tobacco Bright Yellow-2 cells). The team aimed to compare the microtubule
cytoskeleton of plant cells exposed to weightlessness for a shorter period with the microtubule
cytoskeleton of plant cells, which have been exposed to weightlessness for a longer period.
RESULTS
It was found that at near weightlessness during an 8-day space experiment aboard the
International Space Station (ISS), tobacco BY-2 suspension culture cells divided and grew as the
control cells in the on-board 1-g centrifuge and the 1-g ground setup. Their interphase
cytoarchitecture and their cortical microtubule and cellulose micro fibril ordering were also
indistinguishable. Not only did near weightlessness not alter these characteristics, the whole
environment, including radiation and vibrations, also did not affect the processes that are
crucial for plant cell growth and proliferation. These are important and positive results if, in the
future, plants have to be propagated from (frozen) cell culture stocks during long-term space
missions. In general, the results agree with several studies using whole plants (Halstead and
Dutcher 1987; Musgrave et al. 1997; Levine et al. 2001), but contrast with the findings of Sato
and coworkers (1999), who reported, based on electron microscopic observations, that
Nicotiana tabacum stem explants grown in space had reduced microtubule quantities. It was
concluded that plant cells do not need to be organized in a tissue to grow, divide, and organize
their microtubules and cellulose microfibrils in space.
PUBLICATION(S)
Sieberer BJ, Kieft H, Franssen-Verheijen T, Emons AC, Vos JW. Cell proliferation, cell shape, and
microtubule and cellulose microfibril organization of tobacco BY-2 cells are not altered by
exposure to near weightlessness in space. Planta. September 16, 2009;230(6):1129-1140. doi:
10.1007/s00425-009-1010-7.
Sieberer BJ, Emons AC, Vos JW. Culturing immobilized plant cells for the TUBUL space
experiments on the DELTA and 12S Missions. Microgravity Science and Technology. September
2007; 19(5-6):191-194. doi: 10.1007/BF02919480.
These investigations are complete and all results are published.