The mitogen-activated protein kinase GhMPK3 participates in ethylene signaling regulating fiber elongation in cotton (Gossypium hirsutum).

key messageGhMPK3 promotes cotton fiber elongation by phosphorylating GhEIN3cA, which in turn transcriptionally activates GhACO3 to elevate ethylene synthesis. Cotton is an important economic crop worldwide. Understanding the regulatory mechanisms that govern cotton fiber development is essential for enhancing both fiber yield and quality. Mitogen-activated protein kinases (MAPKs) play critical roles in plant growth, development, and physiological metabolism; however, their specific functions in cotton fiber development remain largely unexplored. Our previous research demonstrated that GhMPK3 is predominantly expressed during the elongation of cotton fiber cells and exhibits a sustained high level of phosphorylation. This study reveals that silencing GhMPK3 in cotton fibers impedes fiber elongation. Additionally, GhMPK3 enhances the transcriptional activity of the key ethylene signaling pathway transcription factor GhEIN3cA by phosphorylation to promote the expression of ethylene biosynthesis enzyme GhACO3, thereby facilitating cotton fiber elongation. This investigation elucidates the mechanism through which GhMPK3 mediates the ethylene signaling pathway to regulate cotton fiber development. The findings will aid in refining the regulatory network of cotton fiber development and provide a scientific foundation for improving cotton fiber quality.