The effect of exposure to microgravity on the development and structural organisation of plant protoplasts flown on Biokosmos 9

Abstract

Preparatory experiments for the IML-1 (International Microgravity Laboratory) mission to be flown on the Space Shuttle in January, 1992, were performed on a 14 day flight on Biokosmos 9 (Kosmos 2044) in September 1989. The purpose of the experiment was to study the effect of weightlessness on protoplast regeneration. Problems with late access to the space vehicle meant that the newly isolated protoplasts from hypocotyl cells of rapeseed (Brassica napus L. cv Niklas) and suspension cultures of carrot (Daucus carota L, cv Nobo) had to be stored at 4 degrees C for 36 h prior to the launch of the biosatellite, in order to delay cell wall regeneration until the samples were in orbit. In the flight samples and the ground controls, a portion of the total number of protoplasts regenerated cell walls. The growth of flight rapeseed cells was only 56% compared to the ground control; the respective growth of carrot cells in orbit was 82% of the ground control. Analysis demonstrated that the peroxidase activity and the amount of protein was lower in the flight samples than in the ground controls. The number of different isoenzymes was also decreased in the flight samples. A 54% decrease in the production of cellulose was found in rapeseed, and a 71% decrease in carrot. Hemicellulose production was also decreased in the flight samples compared to the ground controls. Ultrastructural analysis of the cell aggregates from the protoplasts cultured in orbit, demonstrated that hydrolysis and disappearance of reserve starch occurred in the flight cell plastids. The mitochondria were more varied in appearance in the flight samples than in the ground control cells. An increased frequency of the occurrence of folds formed by the plasmalemma together with an increase in the degree of complexity of these folds was also observed. Fluorescence analysis showed a decrease of the calcium content in cell cultures under space flight compared to the ground controls. One general effect of the stay onboard the space vehicle was a retardation of the regeneration processes. Callus cultures obtained from the flight samples grew very slowly compared to callus regenerated from the ground controls, and two years after the Biokosmos 9 flight there appears to be no further growth in the samples exposed to microgravity. Callus cultures from the ground controls, however, continue to grow well. A simulation experiment for IML-l performed in January 1990 at ESTEC (European Space Technology Center), The Netherlands, has resulted in regenerated plants. These observations are discussed and compared to the results obtained on Biokosmos 9.

Effect of simulated and real weightlessness on early regeneration stages of Brassica napus protoplasts

“…Using normal rapeseed hypocotyl protoplasts, a retardation of regeneration was observed on board Biokosmos 9 during a 14 d orbital period in 1989 (Rasmussen et al, 1992). Similar observations were made from protoplast experiments on the space shuttle, for example during the IML-1 mission in 1992, where the same authors obtained evidence that in plant protoplasts exposed to micro-g for 8 d, cell wall formation and division were significantly delayed compared with development under 1 g .…”

“…Line), following standard procedures. Details of the procedures are given by Rasmussen et al (1992) and Skagen et al (1994). The protoplasts were suspended in A medium (Kao and Michayluk, 1981) or MS medium (Murashige and Skoog, 1962) with 2,4-dichlorophenoxy-acetic acid (2,4-D; 4.5 mM), benzyladenine (6-BA; 2.2 mM) and naphthaleneacetic acid (NAA; 0.5 mM) or only with NAA (5.4 mM) to a final concentration of 5X0 Â 10 4 protoplasts per ml medium.…”

“…Several space experiments have been performed with the aim of gaining knowledge about the effect of gravity on basic cell biological processes such as growth, division, and differentiation, using protoplasts as a model system (Rasmussen et al, 1992Iversen et al, 1999). Protoplasts are a convenient model system for comparative studies of the structural and functional aspects of cell wall formation under stationary growth conditions and under the effect of extreme environmental factors known as microgravity (micro-g) conditions on a space vehicle.…”

The effects of spaceflight on soluble protein, isoperoxidase, and genomic DNA in ural licorice (Glycyrrhiza uralensis fisch.)

“…This demonstrates that weightlessness alone could somewhat trigger genomic alterations and result in increased gene expression, while ionizing radiation would enhance the effect of weightlessness. The decreasing effect reported by Rasmussen et al (1992) may have been because they used protoplasts, which are prone to injury during spaceflight.…”

“…In addition, peroxidase activity and the amount of protein were lower in spaceflighted rapeseed (Brassica napus L. cv Niklas) and carrot (Daucus carota L. cv Nobo) than in their ground controls (Rasmussen et al, 1992). However, these effects seemed to be induced only by ionizing radiation plus weightlessness.…”