Indole-3-acetic acid (IAA), the primary auxin in higher plants, plays a crucial role in plant growth and development. While the biosynthesis of auxin in some plant pathogens is well understood, the mechanisms by which plants produce auxin remain largely unclear. Recent studies have identified several genes involved in tryptophan-dependent auxin biosynthesis pathways. Local auxin biosynthesis is essential for various developmental processes, including gametogenesis, embryogenesis, seedling growth, vascular patterning, and flower development. This review summarizes recent advances in understanding auxin biosynthetic pathways and highlights how insights into auxin biosynthesis provide new perspectives on plant development. Key auxin biosynthetic genes, such as YUC and TAA1, are discussed, along with their roles in plant development. The review also explores the relationships among different auxin biosynthesis pathways and the regulation of auxin biosynthesis by environmental and developmental signals. Finally, the potential of using auxin biosynthesis mutants to dissect developmental mechanisms is highlighted.Indole-3-acetic acid (IAA), the primary auxin in higher plants, plays a crucial role in plant growth and development. While the biosynthesis of auxin in some plant pathogens is well understood, the mechanisms by which plants produce auxin remain largely unclear. Recent studies have identified several genes involved in tryptophan-dependent auxin biosynthesis pathways. Local auxin biosynthesis is essential for various developmental processes, including gametogenesis, embryogenesis, seedling growth, vascular patterning, and flower development. This review summarizes recent advances in understanding auxin biosynthetic pathways and highlights how insights into auxin biosynthesis provide new perspectives on plant development. Key auxin biosynthetic genes, such as YUC and TAA1, are discussed, along with their roles in plant development. The review also explores the relationships among different auxin biosynthesis pathways and the regulation of auxin biosynthesis by environmental and developmental signals. Finally, the potential of using auxin biosynthesis mutants to dissect developmental mechanisms is highlighted.