Cell wall changes involved in the automorphic curvature of rice coleoptiles under microgravity conditions in space
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Seedlings of rice (Oryza sativa L. cv. Koshihikari and cv. Tan-ginbozu) were cultivated on board the Space Shuttle STS-95 mission and changes in the morphology and the cell wall properties of coleoptiles were analyzed. In space, rice coleoptiles showed a spontaneous (automorphic) curvature toward the caryopsis in the elongating region. The angle of automorphic curvature was larger in Koshihikari than in a gibberellin-deficient dwarf cultivar, Tan-ginbozu, and the angle gradually decreased during the growth of coleoptiles in both cultivars. The more quickly expanding convex side of the bending region of the rice coleoptiles showed a greater extensibility of the cell wall than the opposite side. There was a significant correlation between the angle of curvature and the difference in the cell wall extensibility between the convex and the concave sides. Both the levels of the cell wall polysaccharides per unit length of coleoptile and the ratio of high-molecular-mass polysaccharides in the hemicellulose fraction were lower in the convex side than the concave one. Also, the activity of (1→3),(1→4)-β-glucanases in the cell wall was higher in the convex side than the concave one. These results suggest that the uneven modifications of cell wall metabolism bring about the difference in the levels and the molecular size of the cell wall polysaccharides, thereby causing the difference in capacity of the cell wall to expand between the dorsal and the ventral sides, leading to the automorphic curvature of rice coleoptiles in space. The data also suggest the involvement of gibberellins in inducing the automorphic curvature under microgravity conditions.
KeywordsAutomorphogenesis Cell wall Coleoptile Microgravity Rice (Oryza sativa L.) Spontaneous curvature
We thank Professor Emeritus Y. Masuda (Osaka City University), S. Kamigaichi, S. Aizawa, I. Yoshizaki and C. Mukai (National Space Development Agency), T. Shimazu and K. Fukui (Japan Space Forum), M. Furukawa (Japan Manned Space Systems), and K. Norwood (Bionetics) for their advice, efforts, and cooperation during the STS-95 mission. The present study was supported in part by Grants-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture; a grant for Basic Research in Space Station Utilization from the Institute of Space and Astronautical Science; and a grant for Ground Research for Space Utilization from Japan Space Forum.
- Cosgrove DJ (1990) Gravitropism of cucumber hypocotyls: biophysical mechanism of altered growth. Plant Cell Env 13:235–241Google Scholar
- Dubois M, Gilles KA, Hamilton JK, Rebers PA, Smith F (1956) Colorimetric method for determination of sugars and related substances. Anal Chem 28:350–356Google Scholar
- Heathcote DG, Chapman DK, Brown AH (1995) Nastic curvatures of wheat coleoptiles that develop in true microgravity. Plant Cell Env 18:818–822Google Scholar
- Hoson T (1993) Regulation of polysaccharide breakdown during auxin-induced cell wall loosening. J Plant Res 106:369–381Google Scholar
- Hoson T (1994) Automorphogenesis of maize roots under simulated microgravity conditions. Plant Soil 165:309–314Google Scholar
- Hoson T, Kamisaka S, Masuda Y, Yamashita M (1992) Changes in plant growth processes under microgravity conditions simulated by a three-dimensional clinostat. Bot Mag 105:53–70Google Scholar
- Inouhe M, Nevins DJ (1998) Changes in the activities and polypeptide levels of exo- and endoglucanases in cell walls during developmental growth of Zea mays coleoptiles. Plant Cell Physiol 39:762–768Google Scholar
- Nakamura T, Saotome M, Ishiguro Y, Itoh R, Higurashi S, Hosono M, Ishii Y (1994) The effects of GA3 on weeping of growing shoots of the Japanese cherry, Prunus spachiana. Plant Cell Physiol 35:523–527Google Scholar
- Pfeffer W (1904) Pflanzenphysiologie, vol 2. W Engelmann, LeipzigGoogle Scholar
- Revilla G, Zarra I, Masuda Y (1988) Molecular weight distribution of hemicellulosic polysaccharides of the cell wall of tall and dwarf rice cultivars, and the effect of GA3. Physiol Plant 72:782–789Google Scholar