Functional analysis of Gossypium hirsutum cellulose synthase catalytic subunit 4 promoter in transgenic Arabidopsis and cotton tissues

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, β-glucuronidase (GUS) activity regulated by a GhCesA4 promoter (−2574/+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 GhCesA4 promoter (−2574/+56) was found in trichomes and root vascular tissues in both cotton and transgenic Arabidopsis. The −2574/−1824 region was responsible for up-regulation of GhCesA4 expression in trichomes and root vascular tissues in transgenic Arabidopsis. The −1824/−1355 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 roots as well as Arabidopsis roots. Exogenous phytohormonal treatments on transgenic Arabidopsis revealed that phytohormones may be involved in the differential regulation of GhCesA4 during cotton fiber development.

Research highlights▶ Spatial regulation of cotton fiber GhCesA4 promoter was similar between cotton tissues and transgenic Arabidopsis. ▶ One upstream region (−2574/−1824) of the GhCesA4 promoter was involved in up-regulating GhCesA4 expression in trichomes and root vascular tissues. ▶ The −1824/−1355 region of the GhCesA4 promoter was involved in down-regulating GhCesA4 expression in vascular tissues. ▶ The −693/−320 region of the GhCesA4 promoter was necessary for basal expression of GhCesA4 in cotton roots as well as Arabidopsis trichomes and roots. ▶ GhCesA4 expression was differentially regulated in transgenic Arabidopsis by NAA, kinetin, and brassinosteroids.