Cellular basis for the automorphic curvature of rice coleoptiles on a three-dimensional clinostat: possible involvement of reorientation of cortical microtubules

Abstract

Coleoptiles of rice (Oryza sativa L.) show a spontaneous (automorphic) curvature toward the caryopsis under microgravity conditions. The possible involvement of the reorientation of cortical microtubules in automorphic curvature was studied in rice coleoptiles grown on a three-dimensional clinostat. When rice seedlings that had been grown in the normal gravitational field were transferred to the clinostat in the dark, cortical microtubules of epidermal cells in the dorsal side of the coleoptiles oriented more transversely than the ventral side within 0.5 h. The rotation on the clinostat also increased the cell wall extensibility in the dorsal side and decreased the extensibility in the ventral side, and induced automorphic curvature. The reorientation of cortical microtubules preceded the changes in the cell wall extensibility and the curvature. The irradiation of rice seedlings with white light from above inhibited microtubule reorientation and changes in the cell wall extensibility, as well as curvature of coleoptiles. Also, colchicine, applied to the bending region of coleoptiles, partially inhibited the automorphic curvature. These results suggest that reorientation of cortical microtubules is involved in causing automorphic curvature in rice coleoptiles on the clinostat.

Hypergravity induces reorientation of cortical microtubules and modifies growth anisotropy in azuki bean epicotyls

“…However, no clear changes in microtubule orientation were observed in parenchymatous cells (data not shown). In rice coleoptiles grown under microgravity conditions simulated by threedimensional clinostat, cortical microtubules on the dorsal side of coleoptiles oriented more transversely than those on the ventral side (Saiki et al 2005). The changes in orientation of microtubules were observed clearly in epidermal cells than parenchymatous cells in clinostatted rice coleoptiles.…”

“…In gravitropism, cortical microtubules in the faster-expanding convex Xank were transverse, whereas the microtubules in the concave Xank showed a longitudinal orientation with respect to the longitudinal axis of the cell (Nick et al 1990;BlancaXor and Hasenstein 1993). Hypergravity promoted reorientation of microtubules into parallel arrays in protoplasts from Nicotiana tabacum (Wymer et al 1996) and Brassica napus (Skagen and Iversen 1999), and under microgravity conditions simulated by three-dimensional clinostat, cortical microtubules on the dorsal side of rice coleoptiles oriented more transversely than those on the ventral side (Saiki et al 2005).…”

Diatoms in space: testing prospects for reliable diatom nanotechnology in microgravity

“…The primary aim of this paper is to propose a program of collaborative research to see if diatoms undergo normal morphogenesis in microgravity. Since the shaping of diatoms (not just mitotic spindle formation) is highly microtubule (MT) dependent 11,45,46,47,48,49,50,51,52 , and MTs polymerize and aggregate differently in microgravity compared to their behavior at 1 G 53,54,55,56 , we can anticipate that diatom morphogenesis might be disrupted, especially since other eukaryotic plant microtubules are disrupted in clinostats 57,58 (as are animal cells, such as osteoblasts 59 ). The potential role of microtubules in diatom morphogenesis 10 has been simulated 11 , though microgravity has yet to be taken into consideration.…”

Patterning of plant cell wall deposition by cortical microtubules

“…In gravity research in plants, microtubules are considered as an important connection between gravity sensing of plant cells and remodelling of the plant cell wall [95][96][97][98] . This concept is supported by the strong link between microtubules and cellulose synthesis [38][39][40] , and the observation that the cell wall is remodelled in altered gravity conditions 89,99,100 .…”