Regulation by Gravity of Ferulate Formation in Cell Walls of Rice Seedlings (Ferulate) - 12.07.16
Ferulate tests the hypothesis that microgravity modifies ferulic acid thereby decreasing the mechanical strength of cell walls. Science Results for Everyone
Does microgravity weaken plant cell walls? The Ferulate experiment aims to answer this question by testing whether space reduces the levels of ferulic acid (a chemical related to vanillin, the flavorful ingredient of vanilla beans) in cell walls and therefore decreases cell wall strength in rice and wheat plants. Results suggest that stronger gravity increases the rigid network structures within wheat cell wall, contributing to more stable cell walls. Results also suggest that certain genes and enzyme activities are involved in the formation of cell wall ferulate networks in rice. Experiment Details
Kazuyuki Wakabayashi, Ph.D., Osaka City University, Osaka, Japan
Takayuki Hoson, Ph.D., Osaka City University, Osaka, Japan
Koichi Soga, Ph.D., Osaka City University, Osaka, Japan
Hidekazu Tanimoto, Nagoya City University, Japan
Kiyohide Kojima, Niigata University, Japan
Genji Kamata, AES, Japan
Atsushi Higashibata, JAXA, Japan
Sponsoring Space Agency
Japan Aerospace Exploration Agency (JAXA)
Japan Aerospace Exploration Agency
ISS Expedition Duration
March 2010 - September 2010
- The Ferulate Experiment tests the hypothesis that microgravity decreases the mechanical strength of cell walls of rice plants by modifying the levels of abscisic acid.
- The polysaccharide composition of the cell wall in gramineous plants, such as rice, maize, wheat, and barley, is distinguished from that in dicotyledons, such as Arabidopsis, pea, and mung bean, which have been used in many space experiments.
Operational Requirements and Protocols
Decadal Survey Recommendations
Information Pending^ back to top
Plants have evolved over millions of years under the force of gravity and developed a cell wall to support their body and keep it upright. Network structures within the cell wall make it resistant to the gravitational force of the earth. In this experiment, the effects of microgravity on the formation of cell-wall network were examined using soft, and weak rice shoots simultaneously grown in darkness under artificial 1 g and microgravity conditions in the Cell Biology Experiment Facility (CBEF) on the International Space Station (ISS). The CBEF facility allowed for plant samples to be grown under microgravity and artificial 1G conditions simultaneously in orbit. After incubation, seedlings were frozen and returned to Earth for study. The germination rate was more than 90% in both in-orbit 1G and microgravity conditions. The length of 1G-grown rice shoots substantially increased from day 4 to day 5. Microgravity did not affect the shoot growth. Measurement of the mechanical properties of cell walls showed that shoot cell walls became stiffer during the 5-day growth period and that microgravity suppressed this stiffening. Typically, the amounts of cell wall carbohydrates, cell wall-bound phenolic acids, and lignin (organic compound which makes cell walls of many plants rigid and woody) in rice shoots increased as the shoot grew, but is was found that microgravity reduced the rise in lignin. Furthermore, the increases in expression levels of some class III peroxidase genes (genes which create rigid plant structures or adapting plants to a more oxygenated environment) were reduced under microgravity conditions, suggesting that microgravity modifies the expression levels of certain class III peroxidase genes in rice shoots, and that this suppression may cause a decrease in cross-linkages within the cell wall architecture. Reduction in intra-network structures contributes to keeping the cell wall soft and loose. These findings suggest that long term microgravity environment might alter the cellular hydrogen peroxide level by which the downstream signaling events including gene expression would be modulated. The results showed, for the first time, that a microgravity environment could suppress the formation of strong cell walls of rice shoots by modifying the expression levels of certain class III peroxidase genes. Taken together, the present results provide evidence that the lack of gravity decreases the mechanical strength of the cell wall of rice (grassy) plants.^ back to top
Wakabayashi K, Soga K, Kamisaka S, Hoson T. Changes in levels of cell wall constituents in wheat seedlings grown under continuous hypergravity conditions. Advances in Space Research. 2005 January; 36(7): 1292-1297. DOI: 10.1016/j.asr.2005.02.066.
Wakabayashi K, Soga K, Kamisaka S, Hoson T. Increase in the level of arabinoxylan-hydroxycinnamate network in cell walls of wheat coleoptiles grown under continuous hypergravity conditions. Physiologia Plantarum. 2005 September; 125(1): 127-134. DOI: 10.1111/j.1399-3054.2005.00544.x.
Wakabayashi K, Nakano S, Soga K, Hoson T. Cell wall-bound peroxidase activity and lignin formation in azuki bean epicotyls grown under hypergravity conditions. Journal of Plant Physiology. 2009 June; 166(9): 947-954. DOI: 10.1016/j.jplph.2008.12.006. PMID: 19195738.
Wakabayashi K, Soga K, Hoson T, Kotake T, Yamazaki TQ, Higashibata A, Ishioka N, Shimazu T, Fukui K, Osada I, Kasahara H, Kamada M. Suppression of hydroxycinnamate network formation in cell walls of rice shoots grown under microgravity conditions in space. PLOS ONE. 2015; 10(9): e0137992. DOI: 10.1371/journal.pone.0137992. PMID: 26378793.
Wakabayashi K, Soga K, Hoson T. Cell wall oxalate oxidase modifies the ferulate metabolism in cell walls of wheat shoots. Journal of Plant Physiology. 2011 November; 168(16): 1997-2000. DOI: 10.1016/j.jplph.2011.05.010. PMID: 21684033.
Wakabayashi K, Soga K, Hoson T. Phenylalanine ammonia-lyase and cell wall peroxidase are cooperatively involved in the extensive formation of ferulate network in cell walls of developing rice shoots. Journal of Plant Physiology. 2012 February; 169(3): 262-267. DOI: 10.1016/j.jplph.2011.10.002. PMID: 22118877.
Ground Based Results Publications
Wakabayashi K, Soga K, Hoson T. Modification of cell wall architecture in gramineous plants under altered gravity condition. Biological Sciences in Space. 2009; 23(3): 137-142. DOI: 10.2187/bss.23.137.