Submitted to: Plant Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/6/2010
Publication Date: 1/3/2011
Citation: Kim, H.J., Murai, N., Fang, D.D., Triplett, B.A. 2010. Functional analysis of Gossypium hirsutum cellulose synthase catalytic subunit 4 promoter in transgenic Arabidopsis and cotton tissues. Plant Science. 180(2011);323-332. Interpretive Summary: 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 studied a gene named GhCesA4 that is essentially responsible for cellulose production in fibers. Because the promoter regions of genes control when and how genes are expressed, we examined the GhCesA4 promoter region consisting of 2,574 nucleotides using techniques of molecular biology, tissue cultures, and transgenic works. As results, we have found that several regions of the GhCesA4 promoter were involved in activating or repressing the expression of GhCesA4. We also demonstrated that several plant hormones regulated GhCesA4 levels in cotton fibers. This information will help researchers to 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: Gossypium hirsutum cellulose synthase catalytic subunit 4 (GhCesA4) plays an important role in cellulose biosynthesis during cotton fiber development. The transcript levels of GhCesA4 are significantly up-regulated as secondary cell wall cellulose is produced in developing cotton fibers. To understand the molecular mechanisms involved in transcriptional regulation of GhCesA4, '-glucuronidase (GUS) activity regulated by a full GhCesA4 promoter (-2,574/+56) or progressively deleted promoters were determined in both cotton tissues and transgenic Arabidopsis. The spatial regulation of GhCesA4 expression was similar between cotton tissues and transgenic Arabidopsis. GUS activity regulated by the full GhCesA4 promoter was found in trichomes and root vascular tissues in both cotton and transgenic Arabidopsis. The -2,574/-1,824 region was responsible for up-regulation of GhCesA4 expression in trichomes and root vascular tissues in transgenic Arabidopsis. The -1,824/-1,355 region negatively regulated GhCesA4 expression in most Arabidopsis vascular tissues. For vascular expression in stems and leaves, the -898/-693 region was required. The -693/-320 region of the GhCesA4 promoter was necessary for basal expression of GhCesA4 in cotton fibers and roots as well as Arabidopsis trichomes and roots. Exogenous phytohormonal treatments on transgenic Arabidopsis revealed that auxin, brassinosteroids, and cytokinin may be involved in the differential regulation of GhCesA4 during cotton fiber development.