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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Cotton Structure and Quality Research » Research » Publications at this Location » Publication #153915
Title: CHARACTERIZATION OF GHRAC1 GTPASE EXPRESSED IN DEVELOPING COTTON (GOSSYPIUM HIRSUTUM) FIBERS

Author
item KIM, HEE - UNIVERSITY OF NEW ORLEANS
item Triplett, Barbara

Submitted to: Biochimica et Biophysica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2004
Publication Date: 7/31/2004
Citation: Kim, H.J., Triplett, B.A. 2004. Characterization of GhRac1 GTPase expressed in developing cotton (Gossypium Hirsutum) fibers [abstract]. Biochimica et Biophysica Acta. Available from: http://www.doi:10.1016/j.bbaexp.2004.06/008

Interpretive Summary: To keep American cotton competitive in the global marketplace continual improvements must be made in both cotton fiber quality and yield. This research is identifying critical events in fiber formation that can lead to these improvements. The majority of each fiber's weight comes from the cell wall, a complex structure composed of many different chemical polymers. In this study, a gene that may helps to determine how cell wall components are deposited was characterized biochemically and compared with similar proteins from the model plant, Arabidopsis. Based on the similarity of the cotton fiber protein to proteins in the model system, we predict that this gene is involved with the process of organizing cell wall materials. This work contributes new knowledge about how the organization of chemical polymers within the fiber wall is regulated. Understanding how this control point is regulated is a central issue for scientists to resolve in order to use molecular genetic techniques in the improvement of cotton fiber quality and yield.

Technical Abstract: Cotton fibers are unicellular trichomes originating from the ovule epidermis. Fiber cells elongate rapidly bounded by a thin primary wall until secondary wall synthesis begins. Cytoskeleton assemply plays an imporotant role in determining fiber cell length and morphology and is developmentally regulared. As in other plant cells, it is not clear how cytoskeletal assembly in fibers is regulated. Recently, several Rac/Rop GTPases in Arabidopsis were shown to regulate isotropic and polar cell growth of root hairs and pollen tubes by controlling assembly of the cytoskeleton. RhRac1 isolated from cottonseeds is a member of the Rac/Rop GTPase family and is abundantly expressed in rapidly growing cotton tissues. GhRac1 shows the greatest sequence similarity to the group IV subfamily of Arabidopsis Rac/Rop genes. Over-expression of GhRac1 in E coli led to the production of a functional GTPase. In contrast to other Rac/Rop GTPases found in cotton fiber, GhRac1 is highly expressed during the elongation stage of fiber development with expression decreasing dramatically when the rate of fiber elongation declines. The association of higihest GhRac1 expression during stages of maximal cotton fiber elongation suggests that GhRac1 GTPase may be a potential regulator of fiber elongation by controlling cytoskeletal assembly.