Cotton is one of the most important natural fibers used in the textile industry worldwide. It is important to identify the key factors involved in cotton fiber development. In this study, zinc finger protein8 (GhZFP8) encoding a C₂H₂ transcription factor (TF) was cloned from cotton. qPCR showed that the transcripts of GhZFP8 in cotton were detected in the leaves and fibers at 3, 6, and 30 days post-anthesis (DPA), but not in the roots, stems, or flowers. The overexpression of GhZFP8 increased the trichome number on the siliques, leaves, and inflorescence, but inhibited the growth. The expression of trichome development and cell-elongation-related genes decreased obviously in GhZFP8 overexpressor Arabidopsis. Indole-3-acetic acid (IAA) and 1-Aminocyclopropanecarboxylic acid (ACC) contents were much higher in GhZFP8 overexpressors than that found in the wild type, but the gibberellin (GA) content was lower. The interference of GhZFP8 in cotton caused smaller bolls and shorter fibers than that of the control. The results of DNA affinity purification (DAP)-seq showed that GhZFP8 could bind to the promoter, exon, intron, and intergenic region of the target genes, which are involved in photosynthesis, signal transduction, synthesis of biomass, etc. Our findings implied that GhZFP8 processed multiple biological functions and regulated the development of cotton fiber.

Lodging resistance is one of the most important traits of machine-picked cotton. Lodging directly affects the cotton yield, quality and mechanical harvesting effect. However, there are only a few reports on the lodging resistance of cotton. In this study, the morphological and physiological characteristics and transcriptome of two upland cotton varieties with different lodging resistance were compared. The results showed that the stem strength; the contents of lignin, soluble sugar and cellulose; and the activities of several lignin biosynthesis-related enzymes of the lodging-resistant variety M153 were significantly higher than those of the lodging-susceptible variety M5330. Transcriptomic analysis showed that the expression level of several genes related to lignin, cellulose, starch and sucrose synthesis, and photosynthesis were significantly up-regulated in the lodging-resistant variety M153, which was consistent with the content determination results of lignin, cellulose and soluble sugar. Silencing two lignin biosynthesis-related genes (GhPAL and Gh4CL) in cotton via VIGS (Virus-Induced Gene Silencing) resulted in reduced lignin content and decreased lodging resistance in cotton. These results suggested that lignin, cellulose and soluble sugar contents were positively correlated with the lodging resistance of cotton, and lignin, cellulose and soluble sugar biosynthesis-related genes can be used as potential targets for improving the lodging resistance of cotton. These findings provide a theoretical basis for the cultivation of cotton varieties with strong lodging resistance in the future.