Submitted to: World Cotton Research Conference Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2007
Publication Date: 9/10/2007
Citation: Kim, H.J., Triplett, B.A. 2007. Cellulose synthase catalytic subunit (CesA) genes associated with primary or secondary wall biosynthesis in developing cotton fibers (Gossypium hirsutum). World Cotton Research Conference Proceedings. 52:205-220. Interpretive Summary: To keep cotton fibers competitive over synthetic fibers in the global market, there is a demand for improving cotton fiber quality. The quality of cotton fibers is determined by fiber length, strength, and maturity that are directly affected by the production of a biopolymer called cellulose. Molecular mechanisms regulating cellulose production have not been well-characterized. To understand the regulation of cellulose production in cotton fibers, we examined the expression levels of a gene named GhCesA that is centrally responsible for cellulose production in fibers. From this study, we discovered that multiple forms of GhCesA exist in cotton fibers and other tissues and that distinct multiple GhCesA genes are involved in the processes of fiber elongation or cellulose production. The research in this manuscript improves our understanding how different GhCesA genes are regulated during fiber development and which GhCesA genes mainly are responsible for cellulose production in cotton fibers. This information helps researchers develop strategies for enhancing cellulose production in cotton fibers, and will ultimately contribute to improved cotton fiber quality. The data are also useful to plant cell wall researchers to understand cellulose production mechanisms for bioenergy production.
Technical Abstract: Cotton fibers are unicellular seed trichomes and consist of almost pure cellulose. During the transition from elongation growth to secondary wall thickening, the rate of cellulose biosynthesis in fibers rises nearly 100-fold. Although the first two cellulose synthase catalytic subunits (CesAs) were isolated from developing cotton fibers, it is not clear how many CesAs are involved in either primary or secondary wall synthesis in fibers, or how these genes are regulated during cell wall biogenesis. Cotton (Gossypium hirsutum) gene sequences from public databases that contained CesA motifs were classified into fourteen distinct CesA genes. The expression pattern of these genes was measured in field grown fibers for two growing seasons using quantitative RT-PCR. The first group of six GhCesA genes is preferentially expressed in elongating fibers, hypocotyls, and roots. The second group of six CesA genes is expressed specifically during the secondary wall thickening stage of fiber development. A third group comprised of two CesAs is expressed throughout fiber development. The results show that most GhCesA genes are developmentally regulated during fiber development, and that distinct multiple CesA genes are involved in either primary or secondary wall cellulose biosynthesis in cotton fibers. Recent progress on understanding the molecular basis for regulation of secondary wall CesA genes will also be discussed.