The bHLH transcription factor GhPAS1 mediates BR signaling to regulate plant development and architecture in cotton

Abstract

Cotton (Gossypium spp.) is the most important natural textile fiber crop in the world. The ideal plant architecture of cotton is suitable for mechanical harvesting and productivity in modern agricultural production. However, cotton genes regulating plant development and architecture have not been fully identified. We identified a basic helix-loop-helix (bHLH) transcription factor, GhPAS1 (PAGODA1 SUPPRESSOR 1) in G. hirsutum (Upland cotton). GhPAS1 was located in the nucleus and showed a strong transcription activation effect. Tissue-specific expression patterns showed that GhPAS1 was highly expressed in floral organs, followed by high expression in early stages of ovule development and rapid fiber elongation. GhPAS1 overexpression in Arabidopsis and BRZ (brassinazole, BR biosynthesis inhibitor) treatment indicated that GhPAS1 positively regulates and responds to the BR (brassinosteroid) signaling pathway and promotes cell elongation. GhPAS1 overexpression in Arabidopsis mediated plant development in addition to increasing plant biomass. Virus-induced gene silencing of GhPAS1 indicated that down-regulation of GhPAS1 inhibited cotton growth and development, as plant height, fruit branch length, and boll size of silenced plants were lower than in control plants. Fiber length and seed yield were also lower in silenced plants. We conclude that GhPAS1, a bHLH transcription factor, regulates plant development and architecture in cotton. These findings may help breeders and researchers develop cotton cultivars with desirable agronomic characteristics.