Cotton Genomics and Genetics 2025, Vol.16, No.1, 1-11 http://cropscipublisher.com/index.php/cgg 1 Research Insight Open Access Research Insights into Hormonal Regulation of Cotton Fiber Elongation Jiamin Wang, Shujuan Wang Hainan Provincial Key Laboratory of Crop Molecular Breeding, Sanya, 572025, Hainan, China Corresponding email: shujuan.wang@hitar.org Cotton Genomics and Genetics, 2025, Vol.16, No.1 doi: 10.5376/cgg.2025.16.0001 Received: 09 Dec., 2024 Accepted: 14 Jan., 2025 Published: 23 Jan., 2025 Copyright © 2025 Wang and Wang, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Wang J.M., and Wang S.J., 2025, Research insights into hormonal regulation of cotton fiber elongation, Cotton Genomics and Genetics, 16(1): 1-11 (doi: 10.5376/cgg.2025.16.0001) Abstract Cotton fiber elongation, a key factor in fiber quality and yield, is regulated by a complex network of phytohormones. Auxin, gibberellins (GAs), brassinosteroids (BRs), ethylene, and peptide hormones promote elongation, while cytokinin and abscisic acid (ABA) act as inhibitors. Key transcription factors such as GhMYB212, GhHOX3, and GhBES1.4 drive fiber growth through hormone signaling and sucrose transport regulation. Crosstalk between hormones, such as auxin-BR and GA-strigolactone interactions, further optimizes fiber elongation. Emerging insights into lipid metabolism (e.g., GhLTP4) and peptide hormones (e.g., GhPSK) reveal additional mechanisms enhancing fiber quality. Future efforts should focus on targeted genetic engineering, hormone pathway optimization, and integrating multi-omics approaches to develop high-quality, resilient cotton varieties, ensuring sustainable production for the textile industry. Keywords Cotton fiber elongation; Plant hormonal regulation; Gibberellins (GAs); Brassinosteroids (BRs); Genetic engineering and breeding 1 Introduction Cotton fiber grows from the epidermis of the ovule. It is actually a single cell that goes through four main stages during development: initiation, elongation, secondary cell wall formation, and the final maturation stage (Lee et al., 2007; Fang et al., 2018). Because these fiber cells grow very long and have many variations, they are often used to study how cells grow larger, how polyploidy forms, and how cell walls are synthesized (Xiao et al., 2019). Among them, the elongation step is the most important, which determines how long the fiber can grow in the end. And fiber length is a key quality indicator in textile production (Tuttle et al., 2015). Whether the fiber can grow long directly affects the yield and quality of cotton. In textile mills, long fibers are more popular. They spin better yarn and higher quality fabrics (Sun et al., 2019; Wang et al., 2021). Fiber elongation is actually a process in which the cell itself becomes larger. This process is not simple and is regulated by both genes and hormones (Cao et al., 2020; Chen et al., 2023). Some hormones, such as auxin, gibberellin, brassinolide and ethylene, can help fibers grow longer. But some hormones, such as cytokinin and abscisic acid, make it difficult for fibers to elongate (Xiao et al., 2019). Understanding these regulatory mechanisms is very useful for us to improve the quality and yield of cotton. This information is important both from a genetic perspective and from an agricultural planting perspective (Li et al., 2020; Zhai et al., 2023). This study aims to comprehensively explore the role of hormone regulation in cotton fiber elongation. We will integrate the latest findings in this field, with a particular focus on the effects of different plant hormones on fiber development. The study will also identify key genes related to hormone biosynthesis and signal transduction pathways, and explore the specific mechanisms of how these hormones regulate fiber elongation. By bringing together existing research results, this study hopes to provide valuable reference and guidance for the genetic improvement of cotton and the development of planting technology. 2 Hormonal Pathways in Plant Development 2.1 Role of hormones in cell elongation Plant hormones are important for cell elongation. Cell elongation is the basis for plants to grow taller or larger. Many hormones can help cells grow longer, such as auxin, gibberellins, brassinolide, ethylene, jasmonic acid, and
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