Development in Altered Gravity Influences Height in Dictyostelium

Morris A Benjaminson, James A Gilchriest, Stan Lehrer

Abstract


We investigated the effects of altered gravity on the life cycle of Dictyostelium discoideum after and during life-long exposure to one of three altered g environments: (1) substrate inverted, parallel and facing the surface of the earth, (2) hyper-g (3) reduced-g. To this end, we measured the height of the final stage of the life cycle, the mature spore-bearing sorocarp. Typically, the sorocarp stands erect and perpendicular to the substrate. In the case of each altered g environment, the control cultures were produced and treated identically to the experimental cultures except for the conditions of their exposure to altered g. Inverted cultures developing and growing in the same direction as the gravity vector had a mean height of 1.84 mm. Their counterpart control cultures had a mean height of 1.64 mm being therefore statistically significantly shorter. Cultures chronically exposed to a hyper (10) g environment produced sorocarps with a mean height of 1.13 mm. These were statistically significantly shorter than their 1 g controls whose mean height was 2.06 mm. Clinorotated (simulated reduced g) sorocarp heights (mean equal to 2.12 mm) were statistically significantly taller compared to their 1 g controls (mean equal to 1.79 mm). The significance level for all the statistical analyses is p< 0.05. Therefore, measurements of the mature stage after life-long exposure to simulated altered gravity show that the final height of that structure is ultimately determined at least partially, by the gravity environment in which development is taking place

References


Albrecht-Buehler, G., 1992. The simulation of microgravity conditions on the ground. ASGSB Bull. 5(2): 3-10.

Athanasius F.M., Hogeweg, P., 2001. Modeling Dictyostelium discoideum Morphogenesis: the Culmination. Bulletin of Mathematical Biology 64: 327-353.

Benjaminson, M.A., and Brown, A.H., 1988. Effects of chronic 5g and 10g centrifugation on Dictyostelium cultures from developmentally homogeneous and mixed inocula. Fourth Annual Meeting, American Society for Gravitational and Space Biology; Washington D.C.: 20-23.

Benjaminson, M.A., 1989a. Gravity response and tropisms in Dictyostelium discoideum: FASEB Conference on Biochemical and Biophysical Mechanisms of Gravity Response; Copper Mountain, Colorado: 25-30.

Benjaminson, M.A., 1989b. Dictyostelium discoideum: Basis for decisions in the design of flight experiments. Fifth Annual Meeting of the American Society for Gravitational and Space Biology, Coco Beach, Florida: 24-28.

Benjaminson, M.A., 1996. Time, Gravity, Energy and Biochronology: A Theory. Gravit Space Biol Bull.: 10:8.

Benjaminson, M.A., 1997. The Dictyostelium life cycle: A sensitive gauge of cellular and organismic response to gravity. Space Life Sciences Symposium: Three Decades of Life Science Research In Space, Washington D.C.: 21-26.

Benjaminson, M.A., Lehrer, S., Gilchriest, J., Schonbrun, L, Madigan, M., 2006. Two Special Instruments for the Study of Simulated Altered Gravity. Gravitational and Space Biology, 20 (1).

Breen EJ, Eliott S, Vardy PH, White A, Williams KL., 1992. Length regulation in the Dictyostelium discoideum slug is a late event Jun 1; 262(3): 299-306.

Brock DA, Gomer RH., 1999. A cell-counting factor regulating structure size in Dictyostelium., Aug 1; 13(15): 1960-9.

Hader, D.P., 1999. Gravitaxis in Unicellular Microorganisms. Adv. Space Res. Vol. 24, No. 6: 843-850.

Okuwa T, Katayama T, Takano A, Kodaira K, Yasukawa H., 2001. Two cell-counting factors regulate the aggregate size of the cellular slime mold Dictyostelium discoideum., Dec.; 43 (6): 735-44.

Kawasaki, Y., Kiryu, T., Usui, K., Mizutani, H., 1990. Growth in the cellular slime mold Dictyostelium discoideum, is gravity dependent. Plant Physiology. 93: 1568-1572.

Kempes, C.P., Dutkiewicz, S. and Follows, M.J., 2011. Growth, Metabolic partitioning, and the size of micro organisms. Proceedings of the National Academy of Sciences of the United States of America. E-pub ahead of print.doc: 1073/pmas.III5585109.

Kopachik W., Size regulation in Dictyostelium., 1982. Apr.; 68: 23-35.

Lehrer, S., 2002. Discussion of Clinostat Theory, Addendum to Clinostat Model D1003 Manual. Self Published.

Loomis, W.F., 1975. Dictyostelium discoideum: A Developmental System. Academic Press, NY.

McNab, B.K., 1984. Energetics: The behavioral and ecological consequences of body size, Florida Entomologist, 67:68-73.

Maeda, Y., Madea, M., 1974. Heterogeneity of the cell population of the cellular slime mold Dictyostelium before aggregation, and its relation to the subsequent locations of the cells. Experimental Cell Research 84: 88-94.

Rajender K. Kamboj, Tak Yee Lam, and Chi-Hung Siu, 1990. Regulation of Slug size by the cell adhesion molecule gp80 in Dictyostelium discoideum., Sept., Vol. 1, 715-729.

Takahashi, A., Ohnishi, K., Takahashi, S., Masukawa, M., Sekikawa, K., Amano, T., Nakano, T., Nagaoka, S., and Ohnishi, T., 2001. Differentiation of Dictyostelium discoideum Vegetative Cells into Spores During Earth Orbit in Space. Advances in Space Research: the official journal of the Committee on Space Research, Vol 28, No: 4: 549-553.

Vasiev, B., Cornelis, J.W., 2003. Modeling of Dictyostelium discoideum slug migration. Journal of Theoretical Biology 223: 347-359.


Full Text: PG. 51-58 -- PDF