Regulation by Gravity of Ferulate Formation in Cell Walls of Rice Seedlings (Ferulate) - 02.15.14
ISS Science for Everyone
Science Objectives for Everyone 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.
Sponsoring Space Agency
Japan Aerospace Exploration Agency (JAXA)
ISS Expedition Duration
March 2010 - September 2010
Previous ISS Missions
- 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.
The sterilized rice seeds were planted on an agar medium, placed in a black polycarbonate culture dish, and stored in a refrigerator to prevent germination before and during the flight until the start of growth experiment in the Kibo module of the International Space Station (ISS). In orbit, seeds were transferred to the Cell Biology Experiment Facility (CBEF) and allowed to germinate and grow under 1G and microgravity conditions in the dark. After incubation, seedlings were frozen and returned to Earth. The CBEF has 2 incubator compartments, a microgravity compartment and an artificial gravity compartment with a centrifuge. The facility allowed for plant samples to be grown under microgravity and artificial 1 G conditions simultaneously in orbit. 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. Analysis of the mechanical properties in the cell walls showed that shoot cell walls obtained from seedlings grown under microgravity conditions for 5 days were loosened as compared with those under 1G conditions. On day 5, the levels of cell wall-bound mono-phenolic acids, such as ferulic acid (FA), in microgravity grown shoots were almost comparable to those in 1 G-grown shoots, while the levels of diferulic acid (DFA) were lower in microgravity grown shoots. Furthermore, cell wall peroxidases activity measurements showed that the activity obtained from micro G-grown shoots was lower than that from 1G-grown shoots. These results suggest that microgravity conditions reduce the activity of cell wall peroxidases in rice shoots, resulting in the suppression of DFA formation, which in turn, may cause the reduction of mechanical strength in shoot cell walls.
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