EFFECTS OF THE SPACE ENVIRONMENT ON THE NUCLEAR STRUCTURE AND FUNCTION OF PLANT
ROOT MERISTEMATIC CELLS GROWN IN MICROGRAVITY (ROOT)
Research Area: Plant Biology
Expedition(s): 7 and 8
Principal Investigator(s): ● Francisco-Javier Medina, Centro de Investigaciones Biologicas,
Madrid, Spain
RESEARCH OBJECTIVES
The main scientific objectives of the Effects of the Space Environment on the Nuclear Structure
and Function of Plant Root meristematic Cells Grown in Microgravity (Root) experiment is to
study the modifications occurring in plant proliferating cells when they have been grown in a
near weightless environment. For this experiment Arabidopsis thaliana has been used, the first
plant species whose genome was totally sequenced.
RESULTS
Conspicuous differences in length were found between seedlings grown at 1 g and the parallel
samples grown under microgravity in that the latter were substantially longer. The causes of
this differential growth were determined by examining the morphology of the root
meristematic cells, with a focus on their nucleoli, in the 2 radial regions of the root meristem,
namely the cortex and stele. While the stele showed longer cells with larger nucleoli in the
longer roots of the flight samples compared with the ground controls, cortical cells from space-
grown seedlings were shorter, more numerous and more densely packed compared to the
ground control. However, nucleoli were smaller and less active in these fast proliferating cells
of the flight sample than in the ground control sample. This lower level of ribosome synthesis
per cell in the flight sample was probably due to an accelerated cell cycle, which resulted in
shortened phases. An altered rate of cell proliferation may have been harmful for the plant and
could be the reason of the reported reduced size of older seedlings grown in space.
Furthermore, in order to explore a possible differential gene expression in proliferating cells
caused by space conditions, 2-dimensional protein electrophoresis was performed on samples
in which fixation was reversed by prolonged storage in buffer. The total proteomic profile of
seedlings showed noticeable differences between the space sample and the ground control.
Immunocytochemical studies, which are currently in progress, will show differences in the
levels as well as in the distribution of relevant nucleolar proteins, known to be regulated in
their expression and in their mechanisms by factors affecting the cell proliferation rate and the
cell cycle progression.
PUBLICATION(S)
Matia I, Gonzalez-Camacho F, Herranz R, et al. Plant cell proliferation and growth are altered by
microgravity conditions in dpaceflight. Journal of Plant Physiology. 2010;167(3):184-193. doi:
10.1016/j.jplph.2009.08.012.